Most congressional Republicans are applauding President Trump for the strategy he outlined for Afghanistan and South Asia Monday night while Democrats are blasting him for withholding key details about an increase in troops.

In a primetime address to the nation, Mr. Trump outlined a plan that would eliminate arbitrary timetables and base further military operations on conditions on the ground. He made clear that while his initial instinct was to withdraw U.S. troops from Afghanistan, he's changed his mind. The president, however, did not explicitly say his strategy will call for more troops to deploy and said he couldn't share specific numbers.

Sen. John McCain, R-Arizona, the chairman of the Senate Armed Services Committee, welcomed the president's plan, saying it is "long overdue" but a good step.

"I believe the President is now moving us well beyond the prior administration's failed strategy of merely postponing defeat," McCain said in a statement. "It is especially important that the newly announced strategy gives no timeline for withdrawal, rather ensures that any decision to reduce our commitment in the future will be based on conditions on the ground."

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Speaker Paul Ryan, R-Wisconsin, said at a CNN town hall after the speech that he's pleased with the president's decision and Senate Majority Mitch McConnell, R-Arizona, said it's "imperative" that General John Nicholson "receive sufficient force levels to accomplish these tasks" that the president presented.

The president's plan didn't please all Republicans, though. Rep. Justin Amash of Michigan tweeted that Mr. Trump "bowed to the military industrial establishment" and "doubled down on perpetual war."

There's nothing hasty about ending America's longest war. @POTUS bowed to military-industrial establishment; doubled down on perpetual war. — Justin Amash (@justinamash) August 22, 2017

Similarly, Breitbart, now under the helm of ousted White House strategist Steve Bannon, ran a story saying that Mr. Trump's "'America First' base was the biggest loser of Trump's speech on Afghanistan Monday night." It continued, "[M]any quickly expressed their disappointment at the business-as-usual address from the president who had once promised to limit American intervention abroad and focus on nation-building at home."

Meanwhile, House Minority Leader Nancy Pelosi, D-California, expressed concern with the president's strategy, suggesting that it could lead to a never-ending war in the region.

"The President's announcement is low on details but raises serious questions," she said. "When President Trump says there will be no ceiling on the number of troops and no timeline for withdrawal, he is declaring an open-ended commitment of American lives with no accountability to the American people."

Other Democrats who've pushed for a new authorization for the use of military force, like Rep. Barbara Lee of California and Sen. Tim Kaine of Virginia, used the opportunity to lobby for a new one again.

"I am deeply troubled by President Trump's failure to outline a comprehensive strategy to bring an end to our nation's longest war," Lee said. "At a minimum, Congress should debate and vote on a new Authorization for the Use of Military Force before we commit to another surge that will keep our troops in Afghanistan for years to come and cost billions more in spending."

Kaine agreed that it should be up to lawmakers to "define the U.S. mission" overseas and update the 2001 AUMF. He also suggested that Mr. Trump's plan is similar to the one carried out by the Obama administration.

"The President broadly outlined a vision tonight, similar to past efforts, and we'll now need to hear specific details from our diplomatic and military leadership to ensure any strategy is comprehensive and will help achieve the aim of ensuring Afghanistan does not become a breeding ground – as it once was – for terrorists that seek to harm us and our allies," he said.