"China will face isolation from the international community if the country does not cooperate in further investigations into the origins of the coronavirus," Sullivan said.
He stressed that "diplomatic preparatory work - rallying the countries of the world, exerting political and diplomatic pressure on China - this is the main part of the efforts that are being made to ultimately put China in front of a tough choice."
Earlier, US President Joe Biden said that he had not come to a conclusion about the source of the coronavirus.