Three South Korean coronavirus test-kit makers have been given the green light to export their devices to the United States, officials said Saturday.

The companies won pre-approval under emergency use authorisation from the US Food and Drug Administration that allows for the products to be sold in America, South Korea's foreign ministry said, without naming the firms. 

The US has more confirmed cases of the coronavirus than anywhere else in the world. Controversy has swirled around the US government's response to the outbreak, with accusations of insufficient preparations.

South Korean President Moon Jae-in said earlier this week that his US counterpart Donald Trump had asked for test kits, although the White House has not confirmed the request. Moon said Trump had promised to help South Korean manufacturers gain regulatory approval.

A South Korean test kit maker told AFP this week that it is now making 350,000 tests a day -- almost as many as the South has used in the entire outbreak so far, and that daily output will increase to a million next month.

Once the hardest-hit country outside China, South Korea appears to have brought its outbreak under control owing to its huge "trace, test and treat" strategy. It has tested more than 380,000 people in a process that is free to anyone referred by doctors or those who have links to a confirmed case.

A diagnosis takes up to six hours, and results are released within a day. More than 50 percent of the country's 9,478 confirmed patients have now recovered thanks to "aggressive tests and active participation in social distancing", authorities said Saturday.

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