The Pentagon is pitching in on work to develop a vaccine for the deadly coronavirus, the military's top uniformed official said on Monday.

"Our military research labs are working feverishly around the horn here to try to come up with a vaccine. So we'll see how that develops over the next couple of months," Joint Chiefs of Staff Chairman Gen. Mark Milley told reporters at the Pentagon.

It's expected to take a year to 18 months to have a fully effective and accessible COVID-19 vaccine, according to top U.S. health officials.

Milley also said that U.S. government military laboratories are "working very consistently, not only on that vaccine but all kinds of things" and that the labs are "working in direct support with health and human services."

Defense Secretary Mark Esper, who also spoke to reporters, said one of the labs was at Fort Detrick, an Army Medical Command installation in Frederick, Md.

As coronavirus continues to spread across the globe, the Defense Department has raced to limit the illness in the ranks. In the past week the department has canceled a joint military exercise with South Korea, restricted access to public areas at Army installations in Italy and ordered all ships that have visited countries in the Pacific region to remain at sea for 14 days.

In addition, U.S. Central Command has ordered all military personnel in Saudi Arabia to stop nonessential travel in the region.

CNN first reported Monday that the U.S. military also canceled a joint military exercise with Israel.

The precautions come as the virus has been recorded in at least 12 states, with two deaths in Washington state. A U.S. service member in South Korea as well and their spouse also tested positive for the illness.

Milley stressed that the virus's overall impact on the military has been "very, very minimal."

"That's not to say it's zero, but it's very, very minimal," he said. "That's not surprising because we have a young demographic, healthy demographic, lots of immunizations, so on and so forth."

He added that in addition to the canceled joint exercise with South Korea, defense officials are "taking a look at some other exercises to see if they need to be modified or changed" due to the threat of the illness.

"Here in the United States we are making all due preparations to protect our bases, camps and stations and also to act in support of Health and Human Services."

In South Korea, where there have been more than 4,300 coronavirus cases recorded, the Pentagon has sent additional medical personnel, equipment and test kits.

Milley also said the Pentagon is planning for all outcomes in relation to the virus.

"The United States military looks at a wide variety of scenarios ... pandemic is the worst case," Milley said.

President Trump, meanwhile, said on Monday that he will be urging pharmaceutical executives to accelerate their efforts to develop a vaccine for the coronavirus. The executives are set to attend a meeting with members of the White House coronavirus task force later in the day.