The US Centers for Disease Control and Prevention (CDC) on Tuesday alerted Americans to begin preparing for the spread of coronavirus in the United States after the flu-like virus surfaced in several more countries.

The announcement signals a change in tone for the US health agency, which had largely been focused on efforts to stop the virus from entering the country and quarantining individuals travelling from China.

"The data over the past week about the spread in other countries has raised our level of concern and expectation that we are going to have community spread here," Dr Nancy Messonnier, director of the CDC's National Center for Immunization and Respiratory Diseases, told reporters on a conference call.

What is not known, she said, is when it will arrive and how severe a US outbreak might be. "Disruption to everyday life might be severe," she cautioned.

Businesses, schools and families should begin having discussions about the possibility that their lives may be disrupted if the virus begins spreading within US communities.

Separately, US Health and Human Services Secretary Alex Azar told a Senate subcommittee there will likely be more cases in the US, and he asked legislators to approve $2.5bn in funding to fight the outbreak after proposing cuts to the department's budget.

"While the immediate risk to individual members of the American public remains low, there is now community transmission in a number of countries, including outside of Asia, which is deeply concerning," Azar said, adding that recent outbreaks in Iran and Italy were particularly worrying.

Major US stock indexes fell again on Tuesday after a sharp selloff on Monday.

Azar said the US government was working closely with state, local, and private sector partners to prepare for mitigating the virus' potential spread in the US.

US Senator Chuck Schumer, however, said President Donald Trump and his administration had been caught "flat-footed" and lacked a comprehensive plan to deal with coronavirus. He called for at least $3.1bn in additional funding to fight it.

"The Trump administration has shown towering and dangerous incompetence when it comes to the coronavirus," said Schumer, the top Senate Democrat. "Mr President, you need to get your act together now. This is a crisis."