US Secretary of State Antony Blinken on Thursday called on China to share information on its Covid outbreak, saying its surging caseload had impacted the world, and he renewed an offer to share US vaccines.

"It is very important for all countries, including China, to focus on people getting vaccinated, making testing and treatment available and, importantly, sharing information with the world about what they're experiencing," Blinken told a news conference.

"It has implications not just for China, but for the entire world. So we would like to see that happen," Blinken said.

Blinken said that China, a frequent US adversary, has not asked for help. Beijing has promoted exports of homegrown vaccines judged by international health experts to be less efficient than US-made ones.

"We're fully prepared to provide assistance to anyone who asks for it if they think it's useful," Blinken said.

Blinken, who plans a visit to Beijing in early 2023 with high US-China tensions easing, said the United States had both a humanitarian and self-interest in limiting China's Covid outbreak.

"Anytime the virus is spreading or is moving around, there is the possibility that a new variant develops, that variant spreads even further, and it comes and hits us or hits other countries," Blinken said.

"And then, as we've seen, there are clear implications for the global economy," he said of Covid policies in China, the world's largest economy after the United States.

China, where Covid-19 was first detected three years ago, had trumpeted a policy of zero cases that included stringent lockdowns. But it abruptly reversed course earlier this month following rare protests.

Many elderly Chinese have never been vaccinated, and crematoriums in some regions of China have been overwhelmed, AFP and other news outlets have reported.