America's special operations forces on the front lines in the war on terrorism are unable to retool and recharge because the elite commando units are in constant demand, a situation that is risking serious readiness challenges for the future, a top commander told Congress Tuesday.

"I closely monitor the parts of our force that are under the most stress," said Army Gen. Raymond Thomas, commander of U.S. Special Operations Command. "There are forces that are meeting themselves coming and going in some regards. Others are in better balance. ... It is a challenge."

Thomas and the top Pentagon civilian overseeing special operations forces were testifying before a House Armed Services Subcommittee. The general cited what he called "unforecasted deployment tempo."

"For instance, in Afghanistan the expectation was that we were going to be finished in 2014, we're now throttling into 2017 and beyond," he said.

Thomas said the unrelenting and unexpected deployments have denied the elite special operations units the chance to recapitalize people and capabilities.

"With budgets going down, what we have had to do essentially, we have had to eat our young," testified Theresa Whelan, the Pentagon's acting assistant secretary of defense for special operations/low-intensity conflict. "We have mortgaged the future in order to facilitate current operations.

"That has impacted readiness, and it has also impacted the development of the force for the future," Whelan said. "And as the threats grow, this is only going to get worse."

The stress on special operations forces has also resulted in some taking their own lives, Thomas testified, though he declined to cite the suicide rate among his troops.

"We are as or more challenged than the other services. I don't want to get into the morbid statistics," Thomas said, "but we are suffering."