WASHINGTON (AP) — President Donald Trump on Tuesday came under growing pressure to respond to allegations that Russia offered bounties for killing American troops in Afghanistan, with Democrats demanding answers and accusing Trump of bowing to Russian President Vladimir Putin at the risk of U.S. soldiers' lives.

Frustrated House Democrats returning from a briefing at the White House said they learned nothing new about American intelligence assessments that suggested Russia was making overtures to militants as the U.S. and the Taliban held talks to end the conflict in Afghanistan. Senate Republicans who attended a separate briefing largely defended the president, arguing along with the White House that the intelligence was unverified.

The intelligence assessments were first reported by The New York Times, then confirmed to The Associated Press by American intelligence officials and others with knowledge of the matter.

White House press secretary Kayleigh McEnany said Tuesday that Trump had been briefed on the intelligence, a day after saying he hadn't because it had not been verified. McEnany added that there were still reservations within the intelligence community on the veracity of the allegations, and insisted that Trump would act to safeguard American forces.

"Make no mistake. This president will always protect American troops," she said.

Majority Leader Steny Hoyer and a small group of other House Democrats met with White House officials as Trump downplayed the allegations and aides said he had not been briefed on them. The Democrats questioned why Trump wouldn't have been briefed sooner and pushed White House officials to have the president make a strong statement about the matter.

House Intelligence Committee Chairman Adam Schiff, one of the Democrats who attended the briefing, said it was "inexplicable" why Trump won't say publicly that he is working to get to the bottom of the issue and why he won't call out Putin. He said Trump's defense that he hasn't been briefed is inexcusable.

"Many of us do not understand his affinity for that autocratic ruler who means our nation ill," Schiff said.

Rep. Mikie Sherrill, D-N.J., a freshman and former Navy helicopter pilot and Russia policy officer, said White House chief of staff Mark Meadows briefed the group. She said the Democrats told the White House briefers that the president should make a statement.

"These are very concerning allegations and if they're true, Russia is going to face repercussions," Sherrill said. "We really pushed that strongly in the meeting."

She wouldn't say how the White House officials reacted or say if the briefers told the Democrats that in fact Trump had been briefed.

Trump and his aides set a high bar for briefing a president since it is rare for intelligence to be confirmed without a shadow of doubt before it is presented to senior government decision-makers.

McEnany declined to say why a different standard of confidence in the intelligence might apply to briefing lawmakers than for bringing information to the president.

Some House Republicans who were briefed by the White House on Monday also said they left with questions.

Texas Rep. Mac Thornberry, the top Republican on the Armed Services Committee, said the panel would "leave no stone unturned" in seeking further information. Rep. Liz Cheney of Wyoming insisted there would be "ramifications" for any targeting of Americans.

But Senate Republicans seemed less concerned and questioned the media reports. Majority Leader Mitch McConnell said he didn't think Trump should be "subjected to every rumor."

"Conclusions, apparently, were not reached," McConnell said.

And Republicans briefed in the White House Situation Room on Tuesday appeared mostly satisfied with the answers they received. Senate Armed Services Chairman Jim Inhofe of Oklahoma said he was "convinced" Trump didn't know about the intelligence. Wisconsin Sen. Ron Johnson, chairman of the Homeland Security and Governmental Affairs Committee, said Trump "can't be made aware of every piece of unverified intelligence."

Senate Intelligence Committee Chairman Marco Rubio said he believed the U.S. was prepared "to do everything possible to protect our men or women stationed abroad, from a variety of threats."

Rubio said new Director of National Intelligence John Ratcliffe, one of the briefers, would be meeting with the Senate panel for a previously-scheduled meeting on Wednesday.

Senators reviewed classified documents related to the allegations Monday evening and Tuesday, including information that was not previously known, according to one aide who was not authorized to discuss the matter publicly and spoke on the condition of anonymity. It was unclear what was contained in the documents.

Some Republican senators did express frustration.

Nebraska Republican Ben Sasse, a member of the intelligence panel, said Monday evening that Congress should focus on finding out who knew what, and when, "and did the commander in chief know? And if not, how the hell not?"

While Russian meddling in Afghanistan isn't new, officials said Russian operatives became more aggressive in their desire to contract with the Taliban and members of the Haqqani Network, a militant group aligned with the Taliban in Afghanistan and designated a foreign terrorist organization in 2012.

The intelligence community has been investigating an April 2019 attack on an American convoy that killed three U.S. Marines after a car rigged with explosives detonated near their armored vehicles as they traveled back to Bagram Airfield, the largest U.S. military installation in Afghanistan, officials told the AP.

Three other U.S. service members were wounded in the attack, along with an Afghan contractor. The Taliban claimed responsibility for the attack. The officials the AP spoke to also said they were looking closely at insider attacks — sometimes called "green-on-blue" attacks — from 2019 to determine if they are also linked to Russian bounties.

One official said the administration discussed several potential responses, but the White House has yet to authorize any.

Intelligence officials told the AP that the White House first became aware of alleged Russian bounties in early 2019 — a year earlier than had been previously reported. The assessments were included in one of Trump's written daily briefings at the time, and then-National Security Adviser John Bolton told colleagues he had briefed Trump on the matter. Bolton declined to comment on that matter, and the White House did not respond to questions.

The intelligence officials and others with knowledge of the matter insisted on anonymity to discuss the highly sensitive matter.

Trump's Democratic general election rival, former Vice President Joe Biden, accused the president Monday of a "betrayal" of American troops in favor of "an embarrassing campaign of deferring and debasing himself before Putin."

"I'm disgusted," Biden told donors, as he recalled his late son Beau's military service. Families of service members, Biden said, "should never, ever have to worry they'll face a threat like this: the commander in chief turning a blind eye."

Asked about the reports on the alleged bounties, Putin's spokesman Dmitry Peskov said Monday, "These claims are lies."

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Associated Press writers Lisa Mascaro, Alan Fram, and Deb Riechmann contributed to this report.