New Delhi’s deal for the Russian S-400 system could limit burgeoning military ties with Washington.

Top Biden administration officials spent the past week being feted by allies in Tokyo and Seoul, rubbing shoulders, bumping elbows, and holding press conference after press conference in front of neatly pressed American, Japanese, and South Korean flags.

But India, the next stop on U.S. Defence Secretary Lloyd Austin’s itinerary, won’t be getting—or giving—the exact same treatment. There’s no “2+2” meeting on the schedule: Secretary of State Antony Blinken has already left the trip for a tense showdown with Chinese officials in Alaska. And New Delhi is a “strategic partner”—not on the same footing as Washington’s full-fledged treaty allies in Northeast Asia.

Austin will still get high-level treatment, meeting with Indian Prime Minister Narendra Modi Friday night before speaking to India’s minister of defence and national security advisor on Saturday, two senior U.S. officials said.

But the distinctions with the rest of Asia will also frame the visit. India has closer cooperation with the United States, allowing American warplanes to refuel at Indian-owned islands, engaging with the so-called Quad countries on coronavirus vaccines, and rebooting long-paused military exercises with Australia.

U.S. defence officials are grappling with one major thorn in the side of the relationship: India is still doing business with Washington’s adversaries, notably by inking a $5.5 billion deal for the Russian S-400 air defence system. U.S. lawmakers and officials warn that the future delivery of the weapon systems could put New Delhi at risk of American sanctions and put a ceiling on how far the relationship can go.

Turkey’s purchase of the same Russian system has already soured ties with the United States and led to American sanctions against a Turkish institution that manages the defence industry. Now, U.S. officials are scrambling to find ways to avoid the same path with India.

“The U.S.-India relationship is largely in sync, but Russia remains one major area of difference,” said Tanvi Madan, a scholar at the Brookings Institution, a Washington-based think tank.

The Biden administration is also under pressure from Capitol Hill as it works to deepen ties with New Delhi. During the trip, Sen. Bob Menendez, chairman of the Senate Foreign Relations Committee, published a letter he wrote to Austin urging the defence secretary to raise concerns about human rights and declining democratic norms in India, and to tell Indian counterparts that the S-400 deal is potentially sanctionable under U.S. law.

Russian arms—which make up a big chunk of India’s arsenal—come with a lower price tag and fewer strings attached than U.S. arms sales, including human rights rules and conditions on transferring the equipment to other countries.

But those weapon purchases have a long logistics tail, keeping India dependent on Russia for maintenance and spare parts for its higher-end defence systems. Then there’s the geopolitics of arms sales, with India’s historic track record of “nonalignment” and carefully balancing relationships across the region as it eyes its rivalry with Pakistan and new tensions with China.

A senior U.S. defence official, speaking on condition of anonymity, said that India’s primary consideration in buying the S-400 was to prevent Pakistan from purchasing it. “That’s a strategic problem the government of India had,” the official said. “They’re committed to that because they have their own national interests. Let’s be blunt.”

While the missile system isn’t yet operational, India is in the process of fielding it. Officials likened the Russian system to something between the U.S. Patriot missile system and the larger, longer-range Terminal High Altitude Area Defence system. There has not been a transaction or event yet that would U.S. trigger sanctions, officials said, which would be applied under a 2017 law, the Countering America’s Adversaries Through Sanctions Act, or CAATSA. The law includes provisions that penalize countries buying Russian weapons systems, and it does not have blanket or country-specific waivers.

“We have urged India, as we do all of our allies and partners, to forgo transactions with Russia that risk triggering sanctions under [CAATSA],” a State Department spokesperson told Foreign Policy. “Broadly speaking, the U.S.-India defence partnership has expanded significantly in recent years, commensurate with India’s status as a Major Defence Partner. We expect this strong momentum in our defence partnership to continue.”

Though India is not a treaty ally, some experts believe Washington should find a way to get around sanctioning New Delhi over the S-400 system.

“The Indians have taken a major strategic shift in recent years in their approach to China, and we’d really be shooting ourselves in the foot to implement CAATSA perfectly as written,” said Eric Sayers, a visiting fellow at the American Enterprise Institute and former special assistant to the commander of U.S. Pacific Command. “That relationship is valuable enough where we can’t let some of these issues like a historic relationship with the Russian government on arms sales get in the way.”

That debate opens broader questions about whether and when Washington should slap sanctions on partner countries that buy up arms from one U.S. rival in a way that strengthens their capability against another U.S. rival.

“It’s an open question how much this will end up affecting partners like India, but also countries like Indonesia and Vietnam who have these legacy relationships with Russia and are not going to give them up any time soon,” Madan said. “In fact, there’s an argument to be made that for America’s Indo-Pacific objectives, you actually want these countries to maintain and build up a certain amount of military capability, and in some cases the U.S. cannot offer that capability.”

Former Defence Secretary James Mattis pushed for a loophole for CAATSA in the National Defence Authorization Act nearly three years ago that would provide nations like India an opportunity to duck U.S. sanctions if they showed they were divesting away from Russian weapons over time. Amendments to CAATSA could provide a way to circumvent slapping any—or at least the most severe—sanctions on India even if it takes control of the S-400 platform.

The United States and NATO-allied countries feared that Turkey’s deployment of the S-400 could erode the advanced F-35 fighter jet’s stealth capabilities by exposing it to the Russian system’s powerful radar, posing a risk to other NATO ally military systems. This prompted the Defence Department to expel Ankara from the advanced fighter jet program in July 2019.

The Trump administration ultimately issued very limited sanctions on Turkey in December 2020, designed in part to spare the country major economic haemorrhaging and prevent a major blow-up with a fellow NATO member. The controversy over India’s S-400 purchase is emblematic of U.S. concerns over the limits it faces to deepening ties with India as a way to counterbalance China.

The United States has tried to use concerted pressure from arms sales and continued instability on India’s border with China to nudge New Delhi away from its traditional “nonaligned” footing, a legacy of the Cold War era. Some U.S. officials believe Modi is slowly and carefully shedding New Delhi’s nonalignment strategy over time, but the Biden administration still has to contend with a partner that views the United States with a degree of scepticism and retains distinct foreign-policy priorities.

When it comes to China, however, the Biden administration sees openings. Indian and Chinese troops engaged in deadly clashes on the Line of Actual Control, the border region between the two powers, in 2020, drastically heightening tensions and pushing New Delhi into closer cooperation with Washington.

Two senior U.S. defence officials said India is also signalling its concern over Beijing’s navy moving between Africa, the Persian Gulf, the Bay of Bengal, and the Strait of Malacca, as well as Chinese build-ups in Sri Lanka, at Pakistan’s Gwadar Port, and in Djibouti.

In late 2020, India allowed U.S. military aircraft for the first time to use its base on India’s Andaman and Nicobar Islands, in the east of the Bay of Bengal, for refuelling stops. Intelligence sharing between the two partners has ramped up, and days before Austin’s visit to New Delhi, the Indian military reportedly decided to procure dozens of U.S.-made armed drones in what could amount to a $3 billion deal. India has also bought U.S.-made Apache helicopters, artillery, and precision-guided munitions in recent years. The Trump administration pushed for India to buy F/A-18 fighter jets, which it is still considering, two former defence officials told Foreign Policy.

But some current and former Pentagon officials became frustrated after they said they came to India’s aid during the Himalayas standoff with China last year, providing cold-weather equipment and other gear to try to support India as it grappled with provocations from the Chinese military.

“Even at that most pressure filled point, the Indian aspirations to collaborate with us were very cool and very limited,” a former defence official said, speaking on condition of anonymity. “There’s a long-term culture there that doesn’t favour that.”

There is still “lingering scepticism” among some Indians over whether deepening ties to the United States is a good idea, even despite all the progress made in recent years, Madan said.

Whether justified or not, “India historically has been sceptical of the U.S. as being unreliable, always attaching strings to relationships with partner countries, and then weaponizing their interdependence,” Madan said.

And despite sending Austin to New Delhi on a high-level visit just months into the administration, President Joe Biden will also have to weigh how hard to push Modi, his Indian counterpart, on human rights concerns, a key foreign-policy priority for the new White House. Those include the nationalist government’s efforts to crack down on free speech and political opposition, and increased discrimination against India’s minority Muslim populations, which international human rights groups are tracking with growing alarm.

Another senior U.S. defence official said the United States routinely raises issues of human rights in meetings with foreign counterparts. For now, U.S. officials seem resigned to gradually improving defence ties between the two countries, without expecting anything like the full-fledged alliances the United States maintains in the Pacific.

“I’m not going to tell you that we see them as somebody that’s going to swing with us and sign a treaty for mutual defence tomorrow,” the senior defence official said. “India has been and will continue to be a 10,000-step journey. We’re on step 12, maybe 15.”