The United States will "immediately" make supplies of vaccine-production material, as well as therapeutics, tests, ventilators and protective equipment available to India as the South Asian giant battles a Covid-19 surge, the White House said Sunday.

Western nations including Britain, France, Canada and Germany have also pledged help as India's coronavirus crisis grows, driving an increase in the global case count in recent days even as the number of vaccines administered worldwide surpassed the one billion mark.

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

"The United States has identified sources of specific raw material urgently required for Indian manufacture of the Covishield vaccine that will immediately be made available for India," a White House statement said.

Washington has also "identified supplies of therapeutics, rapid diagnostic test kits, ventilators, and Personal Protective Equipment (PPE) that will immediately be made available for India," said the statement from National Security Council spokesperson Emily Horne.

But it did not mention whether the United States would send its surplus AstraZeneca shots to India, after top US pandemic adviser Anthony Fauci said on ABC Sunday that it would be considered.

The AstraZeneca jab, 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.

Canadian Foreign Minister Marc Garneau tweeted Sunday that his country was ready to help and had "reached out to Indian authorities to determine how Canada can best support India in its time of need."

A health worker collects a nasal swab sample from a woman to test for the Covid-19 coronavirus in Amritsar, India on April 18, 2021
Representational image of a health worker collecting nasal swab sample from a woman to test for the Covid-19 in India AFP / Narinder NANU

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 such as India to vaccinate their populations.

The worrying scenes out of India have fuelled a backlash against the United States, with celebrities, activists and experts calling for Washington to do more -- including lifting an export ban on raw materials that would allow India to make its own vaccines.

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

Horne's statement came after National Security Advisor Jake Sullivan spoke by telephone with his Indian counterpart Ajit Doval on Sunday.

"Just as India sent assistance to the United States as our hospitals were strained early in the pandemic, the United States is determined to help India in its time of need," the statement said.

Horne said that the US is "pursuing options to provide oxygen generation and related supplies on an urgent basis," and that it is funding a "substantial expansion" of Indian vaccine manufacturer BioE, enabling it to "ramp up to produce at least 1 billion doses of COVID-19 vaccines by the end of 2022."

It will also deploy experts from the Centers for Disease Control and Prevention (CDC) and USAID to work with the Indian government, and help fast-track the mobilization of emergency resources available to India through the Global Fund.