The New York Times reports that members of Congress want intelligence officials to explain the claims that Russia paid a bounty to Afghan militants to kill soldiers who are American or other Coalition forces.

Trump denies that he was briefed. Is it credible that such an important development would not be transmitted to the president?

Democrats and Republicans in Congress demanded on Monday that American intelligence agencies promptly share with lawmakers what they know about a suspected Russian plot to pay bounties to the Taliban to kill American troops in Afghanistan, and threatened to retaliate against the Kremlin.

Speaker Nancy Pelosi and Senator Chuck Schumer of New York, the Democratic leaders of the House and Senate, each requested that all lawmakers be briefed on the matter and for C.I.A. and other intelligence officials to explain how President Trump was informed of intelligence collected about the plot. Mr. Trump has said he was not made aware of an intelligence assessment about the plot; officials have said that it was briefed to the highest levels of the White House and appeared in the president’s daily intelligence brief.

“Congress and the country need answers now,” Ms. Pelosi, Democrat of California, wrote in a letter to John Ratcliffe, the director of national intelligence, and Gina Haspel, the C.I.A. director. “Congress needs to know what the intelligence community knows about this significant threat to American troops and our allies and what options are available to hold Russia accountable.”

In the Republican-controlled Senate, James Inhofe of Oklahoma, the chairman of the Armed Services Committee, said he had asked for information as well and expected to know more on the matter “in the coming days.”

“We’ve known for a long time that Putin is a thug and a murderer, and if these allegations are true, I will work with President Trump on a strong response,” he said in a statement. “My No. 1 priority is the safety of our troops. Right now, though, we need answers.”

The C.I.A. declined to comment on Ms. Pelosi’s request.

Members of Congress were caught off guard on Friday when The New York Times first reported that American intelligence had found that a Russian military intelligence unit had secretly offered bounties to Taliban-linked militants in exchange for killing American troops and their allies in Afghanistan. National Security Council officials met in March to discuss the intelligence, but the White House has taken no known action in response.

The Times further reported on Sunday that American intelligences officers and Special Operations forces in the country had informed their superiors of the suspected Russian plot as early as January, after a large amount of American cash was seized in a raid on a Taliban outpost.

American officials believed that the death of at least one U.S. service member was tied to the bounties, and they are reviewing other combat casualties in search of other potential victims, officials familiar with the matter have said.

The White House has not challenged that the intelligence assessment exists, or that the National Security Council held an interagency meeting about it in late March.

But Mr. Trump and his press secretary, Kaleigh McEnany, have both claimed that he was not briefed on the intelligence report. Mr. Trump said in a tweet late Sunday that “Intel just reported to me that they did not find this info credible, and therefore did not report it to me” or Vice President Mike Pence.

Lawmakers were left uncertain what to believe, and even members of Mr. Trump’s party sounded uneasy on Monday when asked about the president’s statements.

Representative Mac Thornberry of Texas, the top Republican on the House Armed Services Committee, said Mr. Trump’s tweet suggesting he had not been made aware of the reports was “a very concerning statement.”

“Anything with any hint of credibility that would endanger our service members, much less put a bounty on their lives, to me should have been briefed immediately to the commander in chief and a plan to deal with that situation,” he said.