WASHINGTON — The US Army announced a plan to cut 40,000 troops that would impact nearly every Army installation, warning that the reductions could grow if Congress cannot reach a deal to avert sequestration budget cuts.

The Army detailed plans to cut the active-duty force from 490,000 to 450,000 within two years. The end-strength target was made public months ago, but members of Congress were briefed Thursday on the specific bases and units impacted.

Army Director of Force Management Brig. Gen. Randy George, at a press conference Thursday, attributed the decision to fiscal constraints resulting from the Budget Control Act of 2011 and sequestration.

"As you know, these are incredibly difficult choices," he said.

The cuts land hardest in Georgia, Alaska and Hawaii, though George said they affect troops ranging from the infantry, signal, logistics, civil affairs, and military police and trainees.

Big cuts come from restructuring the 3rd Brigade Combat Team (BCT), 3rd Infantry Division, at Fort Benning Georgia, followed by the 4th BCT (Airborne), 25th Infantry Division, at Joint Base Elmendorf-Richardson, Alaska. Each would each shrink from a 4,000-person brigade to a 1,000-person task force.

The 2nd Stryker BCT, 25th Infantry Division, at Schofield Barracks, Hawaii, will convert to an infantry BCT, and the 81st BCT, a National Guard unit on the West Coast, would take over the Stryker equipment.

"There are many other installations taking significant cuts," George said. "All of our installations are providing valuable capability and are important to us."

Asked if Congress could reverse the cuts, George said, "I'm sure they could."

Meanwhile, lawmakers lined up to decry the plan, with Sen. John McCain, chairman of the Senate Armed Services Committee, calling it a "dangerous consequence of a budget-driven strategy."

"With global instability only increasing, and with just 33 percent of the Army's brigade combat teams ready for deployment and decisive operations, there is simply no strategic basis to cut Army force structure below the pre-9/11 level of 490,000," McCain, R-Ariz., said.

"People who believe the world is safer, that we can do with less defense spending and 40,000 fewer soldiers, will take this as good news. I am not one of those people," Rep. Mac Thornberry, R-Texas, chairman of the House Armed Services Committee, said in a statement.

Thornberry called troop level reductions "one of the few places where the military can achieve the savings mandated by defense cuts in the time required. The House Armed Services Committee has consistently warned about the size and pace of reductions in both end strength and defense spending and the negative impact on the country's national security."

The House and Senate had already approved the Army's first cut, to 475,000, in the 2016 defense bills that each has moved through Congress.

The active-duty Army will reach 490,000 soldiers in September and would begin cutting the 40,000 soldiers in October. It would then fall to 475,000 by fiscal 2016, to 460,000 by fiscal 2017 and to 450,000 in fiscal 2018. The Army is also cutting 17,000 civilians.

The reductions amount to a $7 billion savings over four years, George said.

Since 2012, the Army has already cut 80,000 soldiers and shuttered 13 BCTs, including two in Germany and one in South Korea. The Army shrank from from 45 brigade combat teams in 2013 (17 armored, 20 infantry and eight Stryker); to 32 BCTs in 2015 (nine armored, 15 infantry and eight Stryker), and it plans to go to 30 BCTs in 2017 (nine armored, 14 infantry and seven Stryker).

Altogether, the Army will be 21 percent smaller than it was in 2012 if the cuts proceed.

It was not explained where the 17,000 civilians due to be cut would come from, as an analysis was ongoing, George said. He noted that a plan to reduce two-star and higher Army headquarters personnel by 25 percent will account for a significant portion.

In the face of global threats, the Army was quick to say it has forces worldwide, including forces from the 2nd Stryker Cavalry Regiment in Europe, and significant numbers of forces in the Pacific.

Senior Army officials have said, and George repeated, that Army end-strength would fall to 420,000 under sequestration budget cuts; it would then risk being incapable of meeting the nation's national security guidance.

"Unless provisions of the Budget Control Act are changed or reversed, the Army will have to cut an additional 30,000 by 2019," George said, adding later: "Cuts below this would put us at significant risk."

Though some personnel will be forced out, the Army is using attrition to shed "as many as possible."

The Army's No. 2 officer was asked Thursday morning why the service is making these cuts now.

"These are not cuts the Army wants to make, these are cuts required by the budget environment in which we operate," Gen. Daniel Allyn, vice chief of staff of the Army, said. "This 40,000-soldier cut ... will only get us to the program force, it does not deal with the continued threat of sequestration."

Twitter: @reporterjoe