Washington (CNN) The US Army says mitigation efforts to blunt the spread of the coronavirus "have proven insufficient" within the service and it is suspending "non-mission essential functions," including some non-critical training of units in the field and physical fitness training involving large numbers of troops, according to an internal Army directive dated Thursday that was obtained by CNN.

"Mitigation measures taken by the Army to blunt the spread of COVID-19 have proven insufficient," the internal order said. The coronavirus "continues to spread geographically as the number of infected persons continues to rise," it added, saying "additional measures and actions are required to protect the force from further spread of COVID-19."

"The Army, effective immediately, will suspend or modify activities to preserve the force in order to protect the Nation," the directive added.

A total of 280 service members had tested positive for the virus as of Thursday morning, an increase of 53 from the 227 reported on Wednesday. And there are nearly 600 positive cases across the Defense Department, which includes civilians, dependents, and contractors.

"What we're really saying right now, when we look at our commands, we say, 'Do you -- do you really have to do this task that may increase the risk to our soldiers? Or if you have to do that task, then how can you make it a little safer,'" Gen. James McConville, Chief of Staff of the Army told reporters Thursday.

Regarding troops, he said "they still need to do physical fitness, but don't do it in formation. You still need to train on our aircraft, but make sure the people that are training together, you keep the numbers small, and this is how you limit the exposure."

At the same time, any Army units that routinely are available on short notice for any overseas crisis missions will have the highest levels of restrictions introduced, according to the directive. This is known as health condition protection condition "Delta" and is likely to restrict troop's movements so they stay in their homes as much as possible, one Army official told CNN. The Army would not specify which units are under this restriction, but rapid response units typically include special operations units, including Delta Force and potentially elements of the 18th Airborne Corps.

This comes as the Pentagon increasingly is preparing for the possibility of wider outbreaks across the force than originally anticipated. Defense Secretary Mark Esper had originally indicated he would trust local commanders to make decisions.

But as reports grew that bases were still holding large gatherings, he ordered further restrictions across the department on nonessential activities.

Pentagon may limit what it reveals to the public

It is also possible the Pentagon may limit the information it shares publicly about the extent of the outbreak in the coming days if the number of military cases continues to grow.

According to a defense official, at some point in the future the department may decide to stop disclosing the specific locations of where military and DoD personnel have tested positive for the virus if there is a feeling the information could provide adversaries with information about where military readiness may be impacted.

"As the number of cases have ticked up in recent days this has become a concern for the future if there was to be such a significant increase in any particular geographic area that units could be out of commission," the defense official said, adding "we are not there yet," the official said regarding the possibility of limiting public information.

"Unit level readiness data for key military forces is information that is classified as a risk to operational security and could jeopardize operations," Alyssa Farah, a Pentagon spokesperson said in a statement. "If at some point in the future, a commander believes that the coronavirus could affect the readiness of our strategic deterrent or strategic response forces we would understandably protect that information from public release and falling into the hands of our adversaries."

On Wednesday, the Pentagon confirmed that Defense Secretary Mark Esper had ordered a 60-day freeze on all overseas US troop movements, affecting 90,000 scheduled deployments, in one of the latest measures to fight the spread of the virus. The order exempts patients such as those aboard the Roosevelt, among others.

Esper also raised the health protection status for all defense installations worldwide, limiting access and encouraging teleworking.

Despite social distance measures being taken across the department, as they are across the nation, Joint Staff Surgeon Brig. Gen. Paul Friedrichs told reporters at the Pentagon on Wednesday, "we think that we're going to continue to see this -- no surprise -- continue to grow" in the next three weeks, the farthest out they are able to model.

President Donald Trump has said he wants to have the economy opened back up by Easter.

"We think the best way to limit that growth or to mitigate that growth are the measures that we've been talking about," said Friedrichs. "I don't think there's a great deal of value in speculating on a particular date."