The United States has taken decisive action to protect Americans from the threat of a fast-moving coronavirus while offering help to China, President Donald Trump said on Sunday, but a key adviser said Beijing had not accepted the offers of assistance.

Trump appeared to downplay concerns about the flu-like virus that has killed more than 300 people in China and spread to more than two dozen countries, telling Fox television in an interview, "We're gonna see what happens, but we did shut it down, yes."

Concerns about the virus spurred the United States to declare a public health emergency and bar entry to foreign nationals who have recently visited China.