WASHINGTON — Defense Secretary James Mattis on Tuesday promised to deliver a new military strategy for Afghanistan to lawmakers by mid-July, a timeline months behind what some members of Congress had anticipated.

Mattis, appearing in front of the Senate Armed Services Committee, said he hoped to be able to brief senators on the new strategy for America's almost 16-year-old war in the next few weeks.

"We are not winning in Afghanistan," Mattis he told lawmakers. "We will correct that."

But SASC chairman Sen. John McCain, R-Ariz., expressed frustration that the strategy is still unfinished, after promises from President Trump that a new play for America's longest war would be finished in the first few months of the new administration.

"We can't keep going like this," he warned. "You can't expect a stable budget if you don't give us a strategy."

McCain also pledged that if the White House and Pentagon don't offer their own plan for Afghanistan, "you're going to get a strategy from us."

Rumors of a U.S. military build-up in Afghanistan have circulated around Capitol Hill for months, since the commander of United States Forces Afghanistan in February testified that several thousand more troops will be needed to break the "stalemate" in the fight against terrorist groups there.

On Monday, Mattis told House lawmakers that military officials are taking a "regional approach" to the Afghanistan fight, and are in the final stages of presenting that plan to Trump. He told senators Tuesday that military officials are taking steps to make sure the delay in the new strategy is not endangering U.S. troops.

Mattis acknowledged the U.S. military mission in Afghanistan has entered "a strategy-free time" but said rushing the new plan could risk disaster.

McCain, who has been a frequent critic of the Trump White House’s operations, told Mattis that much of the new administration’s national security planning is "beyond your control" but said the new strategy is needed as lawmakers finalize their budget plans for the upcoming fiscal year.

"Congress owes the American people a strategy," the Arizona senator said, adding that the families of three U.S soldiers killed in Afghanistan last weekend "know we don’t have a strategy now."

About 8,500 U.S. troops and another 5,000 other foreign allies are still stationed in Afghanistan, even though the official combat mission there ended in 2014. Nearly 2,400 U.S. troops have been killed in fighting in Afghanistan since 2001.

Leo Shane III covers Congress, Veterans Affairs and the White House for Military Times. He can be reached at lshane@militarytimes.com

Aaron Mehta is Associate Editor and Senior Pentagon Correspondent for Defense News. He can be reached at amehta@defensenews.com.