The White House notified airlines it is mulling a temporary ban on flights from China to the U.S. as the deadly coronavirus continues to spread in parts of the world, sources told CNBC on Tuesday.

No timeline on when the flights could be suspended was given.

The report comes as United Airlines announced Tuesday it is suspending 24 U.S.-China flights, beginning in the first week of February.

The airline said in a statement:

Due to a significant decline in demand for travel to China, we are suspending some flights between our hub cities and Beijing, Hong Kong and Shanghai beginning February 1 through February 8. We will continue to monitor the situation as it develops and will adjust our schedule as needed.

Leading the charge to ensure further precautions are taken in the skies is Sen. Tom Cotton (R-AR), who called on the Trump administration to enact a “targeted travel ban” on China as concerns mount over the virus outbreak.

Cotton wrote in a letter to Secretary of State Mike Pompeo, HSS Secretary Alex Azar, and acting Homeland Security Director Chad Wolfe:

Given the latest developments and the many unknowns about this virus, we ought to follow Benjamin Franklin’s maxim: an ounce of prevention is worth a pound of cure. America is blessed with world-leading researchers and laboratories on the cutting edge of medical science and epidemiology. Working in tandem with them, I’m confident our federal research agencies can develop a vaccine in record time.”

Cotton’s effort to see that the White House implements a travel ban on China was first reported by Breitbart News.

The U.S. is ramping up its response to the 2019 novel coronavirus as it continues to spread, U.S. government officials said Tuesday, as they expand airport screenings and develop potential vaccines and drug treatments for the disease.

Multiple agencies are engaged in efforts to stem the spread of the virus beyond the five initial confirmed U.S. cases, all of which involved people who had traveled to Hubei province in China, ground zero for the virus.

The CDC on Tuesday announced plans to expand screening of travelers from China for the virus from five to 20 international airports across the country, and United Airlines became the first U.S. carrier to cancel flights to China as it suspended 24 flights scheduled for the first week of February.

“To better protect the health of the American public during the emergence of this novel coronavirus and based on evolving information from China, CDC has reassessed its entry strategy,” CDC director Robert Redfield told reporters at a press conference.

The CDC’s latest announcement comes as the virus death toll in mainland China has risen to 132, while cases have surged to 5,974.

The UPI contributed to this report.