WASHINGTON — Top Army and Marine Corps generals warned lawmakers their combat readiness is ebbing and expressed concern they would be unable to fight and win another war in the midst of budget cuts, two wars and heightened global threats.

Gen. Robert Neller, the Marine commandant, said his service is supplying trained and ready troops to regional combatant commanders but would be hard-pressed to rapidly respond to another major crisis — a significant statement as the US stares down threats from an aggressive Russia, a rising China, a belligerent North Korea and an extremist-sponsoring Iran.

"Our ability to meet other regional requirements for major contingency plans, we would be able to do that, but we probably would not be able to do that in the time frame that the current plans call for us to arrive to participate in that conflict," Neller told the House Armed Services Committee.

The Marines would "surge" in such a fight, Neller said, and "provide the best, ready force that we can because that’s what you expect from your Marine Corps."

Army Chief of Staff Gen. Mark Milley said the Army can meet regional combatant command requirements and do counterterrorism and counterinsurgency missions. But the four-star had "grave concerns" that fighting a "higher-end" foe, such as China, Russia, Iran and North Korea, risks failure.

"If that were to happen, I would have grave concerns about the readiness of our force: to deal with that in a timely manner," Milley said. "The cost in terms of time, troops and the ability to accomplish military objectives would be very significant."

Milley and the other service chiefs who testified gave the panel risk assessments in a separate, closed session.

× Transitioning out of the service? Sign up for the Rebootcamp Newsletter to receive helpful information on education, employment and entrepreneurship. Thanks for signing up. By giving us your email, you are opting in to the Rebootcamp Newsletter.

"The United Sates Army right now, you can take it to the bank, is ready to fight ISIS, al-Qaeda, al-Nusra and any other terrorist group," Milley said, using an acronym for the Islamic State group. "When we talk about risk, we're talking about great-power war with one or two countries: China, Russia, Iran and North Korea."

"We can collectively roll the dice and say those days will never come and that's a course of action; that is not a course of action I would advise," Milley said. "There is a high level of risk associated with those contingencies right now."

The military's anti-terrorism and counterinsurgency focus of the last 15 years has shortchanged the Army's training and preparedness to fight high-end threats, hybrid threats, enemy artillery and enemy electronic warfare, Milley said.

The Army is also stretched. As the largest of the armed forces, it tackles 46 percent of demand from regional combatant commands and has suffered the majority of the casualties over the last 15 years, Milley said.

"So you've got the largest force, largest demand, the largest stress and the least budget," Milley said. "All of that is cumulative on the United States Army. We'll execute the missions given to us, but it does come with risk."

Army Secretary Patrick Murphy said the service's 2017 budget is "minimally adequate," but the service is taking steps to shore up readiness. It is expanding its combat training centers to double the number of National Guard units attending.

In the Marine Corps, deployment rates are similarly stressing people and equipment, particularly aviation platforms, which Neller said are undergoing a widespread overhaul. The service needs to repair old aircraft — an activity that is fully funded in the 2017 budget proposal — and buy new aircraft.

Committee Chairman Mac Thornberry, R-Texas, touted the rising number of military aircraft accidents as a symptom of an underfunded military and waning readiness. Both Neller and Milley said they were concerned by the trend.

The Army's mishap rate rose from 1.52 per 100,000 flight hours in 2014 to 1.99 in 2016, Thornberry said. The Marine Corps' mishap rate climbed from an annual average of 2.15 mishaps per 100,000 flying hours of the last ten years to 3.96 in 2016.

The Marine Corps was closely tracking the accidents, but the Marines, Neller said, "don't have enough airplanes to meet the training requirements for the entire force."

According to a committee aide, Thornberry is mulling further action on the issue and sees it as linked to maintenance and training shortfalls.