US will consider its response if China refuses to live up to its international obligations on COVID-19: Sullivan

"We are not, at this point, going to issue threats or ultimatums. What we're going to do is continue to rally support in the international community," Sullivan told CNN in an interview.

"And if it turns out that China refuses to live up to its international obligations, we will have to consider our responses at that point, and we will do so in concert with allies and partners," Sullivan said when asked if the US is considering action against China to increase the pressure.

There are two tracks that the Biden Administration is operating on in terms of trying to get to the bottom of how COVID-19 came into the world.

"One track is an intelligence community assessment that President (Joe) Biden ordered. That has a 90-day clock on it. And, in August, the intelligence community will report back,” he said.

"The second track is an international investigation led by the World Health Organisation, for which President Biden has rallied Democratic partners to say there must be access to China to be able to get the data necessary to understand what happened here,” he said.

Sullivan said that the Administration is in the process of using its own capacities, own capabilities to begin to develop a clearer picture. "Then secondly, in order to build the kind of international consensus around this issue that will be required to put additional pressure on China, that takes diplomatic spadework," he said.

"It''s spadework the president carried forward in a major way at the G7, getting for the first time something the last administration could not get, which was the democratic world speaking out with one voice on this issue. And then we will take it from there,” he said.

Reiterating that the US is not going to simply accept China saying no, he said: “But we will work between now and when this second phase of the WHO investigation is fully under way to have as strong a consensus in the international community as possible, because it is from that position of strength that we will best be able to deal with China.”The origins of the COVID-19 remain a widely debated topic, with some scientists and politicians maintaining that the possibility of a lab leak of the deadly virus exists.

China''s Wuhan Institute of Virology (WIV) is near the outbreak''s known epicentre of Huanan Seafood Market in Wuhan, where the virus first emerged in late 2019 and became a pandemic. More than 178 million confirmed cases have since been confirmed worldwide and at least 3.86 million deaths reported.

China has been accused of withholding raw data and access to sites that would aid deeper investigation into how the virus came into being, and how it first spread.

Scientists believe that the virus is likely to have passed from animals to humans, but there remains a possibility that it may have escaped from the Wuhan Institute of Virology, which investigates other coronaviruses.

Biden last month directed the country’s intelligence agencies to report in the next three months on whether COVID-19 emerged from an animal or during a laboratory accident.

However, Beijing has maintained there is no connection between the pandemic origins and the Wuhan lab and sought to dismiss the issue of a possible leak as an “absurd story”.

China asserts that the COVID-19 broke out in different places in the world and China only reported the virus first.