The United States will consider sending surplus AstraZeneca vaccines to India, as backlash over its stockpile grows and the South Asian giant reels from a Covid-19 surge, top US pandemic advisor Anthony Fauci said Sunday.

Western nations including Britain and Germany have pledged help as India's coronavirus crisis grows, driving increases in global case numbers in recent days even as the number of vaccines administered globally surpasses the one billion mark.

Worst-hit in the country of 1.3 billion people was Delhi, with reports of overwhelmed hospitals, severe oxygen and medicine shortages and patients' families pleading for help on social media.

"We really need to do more. I don't think you can walk away from that," Fauci told ABC's "This Week" news program.

The United States has around 30 million doses of the low-cost AstraZeneca vaccine that are not approved for use in the country, and Fauci said the idea of sending them to India will be "something that is up for active consideration."

He also said the United States is discussing "really ramping up what we can do on the ground, oxygen supplies, drugs, tests, PPE, as well as taking the look into the intermediate and long run about how we can get vaccines to these individuals, both immediately now, as well as in the situation where you help them to be able to essentially make vaccines themselves."

He spoke a day after US Secretary of State Antony Blinken said Washington was "working closely with our partners in the Indian government, and we will rapidly deploy additional support to the people of India and India's health care heroes."

The AstraZeneca vaccine, along with the single-shot Johnson & Johnson vaccine, is suspected of causing very rare but serious blood clots in a handful of cases, but is approved for use in many countries including India.

Experts have long warned that no one will be safe from Covid-19 until everyone is -- including those in the developing world, making it in the global interest for wealthier countries eager to move past the pandemic to help large, lower-income nations like India to vaccinate their populations.

The grim scenes from Delhi fuelled a backlash against the United States online, with celebrities, activists and experts calling for Washington to do more -- including to lift an export ban on the raw materials that would allow India to make its own vaccine.

Writer Salman Rushdie, in a tweet addressed to US President Joe Biden, said "the US has something like a vaccine glut. India is in dire straits. Please overturn this export ban ASAP."

Fauci said the "bottom line" is that "it's a terrible situation that's going on in India and other low- and middle-income countries. And there is more we can do."

"And I believe you will see shortly that all these things that we're talking about are on the table, and we will be moving towards that," he said.