US President Trump has appointed his Vice-President Mike Pence to coordinate the government response to the coronavirus outbreak.
Both men told a White House news conference that the risk to the American people remained very low.
The announcement came as new cases of Covid-19, the infection caused by the Wuhan coronavirus, continue to spread at a rapid pace around the world.
Sixty cases have so far been reported in the US.
Minutes after the White House news conference, the authorities confirmed another US case of Covid-19.
Addressing the press, Mr Trump expressed confidence that the US would be able to handle coronavirus.
“We’re very, very ready for this,” Mr Trump said. Researchers were “rapidly developing” a vaccine, he said.
The highest-ranking career official at the Centers for Disease Control and Prevention delivered a slightly different message from the same podium in the White House briefing room: Not so fast.
“Our aggressive containment strategy here in the United States has been working,” Principal Deputy Director Ann Shuchat said. “However, we do expect more cases, and this is a good time to prepare.”