After years of improving relations between Washington and New Delhi, friction has started to rise as irritation with India’s protectionism mounts and concerns increase over the Hindu nationalist political agenda being pursued by Narendra Modi.

When the Indian prime minister and US president Donald Trump jointly appeared at an Indian-American political rally in Houston in September, it was a testament to how once-fraught US-India relations had been transformed. The two countries have steadily deepened their security and defence ties over the past decades as the US looked to the South Asian nation as a strategic counterweight to China.

But despite their high-profile joint appearance then, a bipartisan consensus that the US and India are natural allies has begun to show signs of eroding.

Many in Washington have been taken aback that Mr Modi’s ruling Bharatiya Janata party seems intent on focusing its political energy on divisive moves to reshape India’s polity, despite being in the midst of a severe economic slowdown: growth has tumbled for six consecutive quarters to a six-year low of 4.5 per cent.

India’s recent adoption of a new citizenship law that critics say discriminates against Muslims, the harsh measures used to suppress protests against it and protracted internet restrictions and high-profile political detentions in the Muslim-majority Kashmir region have prompted even longtime US admirers to question the country’s direction under Mr Modi’s leadership.

“There is definitely a reputational fallout [for] India from all of this,” Nirupama Rao, India’s former ambassador to the US, told the Financial Times. “When people read the telegrams or dispatches out of India, there is certainly a sense that there is this kind of shift — a bend in the river — now.”

Richard Haass, president of the Council on Foreign Relations, a non-partisan think-tank, recently warned that “the creeping Hinduisation of India risked creating a serious problem where little or none existed”. He added that India’s past success was partly due to its secular, democratic nature.

“What happened with Kashmir and now this [citizenship] bill puts this at risk,” he said.

André Carson, one of three Muslim US congressmen, warned that under Mr Modi’s leadership India “continues to veer down a dangerous path”. He denounced the new citizenship rules as “yet another attempt to effectively reduce Muslims in India to second-class citizens” and to “strike at the heart of India’s founding tradition as a multicultural society”.

New Delhi has responded testily to the growing chorus of criticism. Its foreign ministry has lashed out at the US Commission on International Religious Freedom, which criticised the new citizenship rules, saying the commission was “guided only by its prejudices and biases on a matter in which it clearly has little knowledge”.

India has hired a Washington-based lobby and public relations firm, Cornerstone Government Affairs, to offer “strategic counsel, tactical planning and government relations assistance” in an attempt to help it handle its relations with the US, regulatory filings show.

Pramila Jayapal, an Indian-American congresswoman from Seattle, is pushing a bipartisan resolution urging New Delhi to restore Kashmir’s internet services and free hundreds of Kashmiri political and civil society leaders who have been detained without charge since August.

During a visit to Washington last month, S Jaishankar, India’s foreign minister, cancelled a scheduled meeting with congressional leaders due to Ms Jayapal’s plan to attend, drawing fierce criticism from top Democrats.

Senator Bernie Sanders, a Democratic presidential candidate, posted on Facebook that “shutting out US lawmakers who are standing up for human rights is what we expect from authoritarian regimes — not from India”.

Ms Jayapal said Mr Jaishankar’s decision to cancel the meeting “furthers the idea that the Indian government isn’t willing to listen to any dissent at all”.

Even before Mr Modi’s re-election, friction was already building. Recent economic policy changes have hit large US e-commerce companies that invest in India, and New Delhi’s insistence that the data gathered from Indian users by US tech companies should be stored in India has also raised concerns.

Many in Congress have begun to fret that India is moving away from its commitment to secularism and protection of minorities that underpinned the oft-repeated assertion that the US and India were bound by “shared values” as well as common strategic interests.

“We always touted India as a beacon for other multi-ethnic democracies looking to balance democracy with diversity,” said Milan Vaishnav, South Asia director at the Carnegie Endowment for International Peace. “Now it seems to be fundamentally reneging on some of those core principles that it signed up to.”

But for all for all the public expressions of dismay, Rudra Chaudhuri, author of the book Forged in Crisis: India and the United States Since 1947, said the current frictions were unlikely to undermine the logic of strong bilateral relations between the two countries, given their shared preoccupation with China

“There is an overarching argument in the US that India is key because of China, and that argument has a lot of weight even today,” said Mr Chaudhuri. “At the top level of policy making, there is not a collective view that India is less democratic today than it was five years ago. This is about hedging your bets and engaging in perception management.”