The White House has sought to play down reports it knew Russia had paid the Taliban bounties to kill US troops, promising to brief Democrats after being accused of only sharing information with President Donald Trump's fellow Republicans.
Trump administration officials said there was no consensus on the underlying intelligence among US agencies and Trump had not been made aware of it.
But two Republican lawmakers said they remain concerned after hearing details from the White House at a meeting on Monday.
"It has been clear for some time that Russia does not wish us well in Afghanistan. We believe it is important to vigorously pursue any information related to Russia or any other country targeting our forces," Representatives Mac Thornberry and Liz Cheney, who attended the meeting, said in a statement.
The New York Times and Washington Post broke the story, with the Post reporting on Sunday that several American soldiers were believed to have died as a result of the program, which the Kremlin has denied.
Intelligence officials were still investigating the matter, Director of National Intelligence John Ratcliffe said.
"Unfortunately, unauthorised disclosures now jeopardise our ability to ever find out the full story," he said in a statement.
That did not appear to satisfy House Speaker Nancy Pelosi, who said after speaking with Ratcliffe and CIA Director Gina Haspel that "many serious questions remain".
Several Democrats in the House of Representatives will hear details from the White House on Tuesday morning, an aide said.
The newspaper reports, suggesting Trump may have ignored a threat to US troops as he seeks to improve relations with Russia, could damage Trump as he seeks re-election on November 3.
Citing unidentified sources, the New York Times reported on Friday that Trump had been notified of the intelligence and the National Security Council discussed the problem at an interagency meeting in late March.
White House spokeswoman Kayleigh McEnany denied Trump was briefed and said there was "no consensus within the intelligence community".
Trump said on Sunday that US intelligence officials told him they had not informed him of the purported program because the information was not credible.
Four US government sources confirmed to Reuters the existence of classified US intelligence reports suggesting that a Russian military intelligence unit had offered bounties to Taliban-linked militants to kill US and allied forces in Afghanistan.
The sources indicated US government agencies and experts on balance believed the intelligence reporting to be credible.
The Kremlin on Monday dismissed the reports as "lies".
The Republican lawmakers were briefed on Monday by Ratcliffe, White House Chief of Staff Mark Meadows and national security adviser Robert O'Brien.
The Post said the intelligence on the bounty scheme stemmed from US military interrogations of captured militants and was passed up from US Special Operations forces in Afghanistan.
The Times reported US intelligence officials believe at least one American military death stemmed from the bounties.