Washington: After the fourth US military aircraft carrying much-needed life-saving supplies landed in India amid the COVID-19 pandemic, Defence Secretary Lloyd Austin on Wednesday described it as a heroic effort from all those involved.

"So far, we've sent 4 grey tails to India, containing 1 million Rapid Diagnostic Tests, 545 Oxygen Concentrators, 1,600,300 N95 masks, 457 Oxygen cylinders, 440 regulators, 220 pulse oximeters and 1 Deployable Oxygen Concentration System," Mr Austin tweeted with three pictures of the US military aircraft in India.

"It's been a heroic effort from all involved," said the defence secretary.

Pentagon Press Secretary John Kirby told reporters that this is just part of the whole-of-government response to "our friends" in India.

"We remain in communication with them to see if there are other ways we can help them defeat COVID as we all move forward," he said.

Most of these supplies are being procured by the Defence Logistics Agency (DLA) at the request of USAID and the US Embassy in India, which are coordinating with the Indian government on the requirement related to life-saving medical supplies.

According to the Pentagon, the agency has been tasked to provide 15 million N95 masks, one million test kits and 704 oxygen concentrators in support of the US Agency for International Development-led effort.

"We remain closely integrated with the White House, National Security Council, the Joint Chiefs of Staff and USAID to help clarify ways DLA can assist," Dave Kless, the agency's executive director of operations, said.

The DLA is also standing by to provide other supplies to India if directed. It has 14 field hospitals pending shipment to US Southern Command that could be redirected to India if requested, the Pentagon said.