ABC News and The New York Times quoted unidentified officials saying that Russia was developing a nuclear, space-based anti-satellite weapon.

According to officials quoted in the Times, Russia has not yet deployed such a capability.

In public, officials said there was no need for panic -- but refused to give details, only issuing cryptic statements about a serious matter, which is set to be discussed in a closed-doors meeting between congressional leaders and the White House on Thursday.

The first inkling of something unusual came from US House Intelligence Committee chairman Michael Turner, who abruptly issued a statement referring to a "serious national security threat."

"I am requesting that President (Joe) Biden declassify all information relating to this threat so that Congress, the administration and our allies can openly discuss the actions necessary to respond to this threat," he said.

Unidentified sources told NBC and CNN the threat was a "highly concerning" Russian military capability, without providing further details.

Turner and his Democratic counterpart Jim Himes said in a letter to lawmakers the panel had "identified an urgent matter with regard to a destabilizing foreign military capability that should be known by all congressional policymakers."

They said the committee had voted on Tuesday to make classified information available in a secure location for review by lawmakers until Friday.

Himes urged caution, however, in a separate statement in which he described the intelligence as "significant" but not "a cause for panic."

The Republican House speaker, Mike Johnson, also urged caution, telling reporters at the Capitol that "there is no need for public alarm."

White House National Security Advisor Jake Sullivan signaled frustration that Turner had gone public ahead of briefing already planned for Thursday.

Sullivan said he would be meeting with the four House members in the "Gang of Eight" group of party leaders and top intelligence committee members.

The drama played out with Biden and the Republican-led House at an impasse over a White House request for $60 billion in military aid to help Ukraine's defense against the Russian invasion entering its third year.

Johnson -- who has repeatedly warned he will not address allies' security until America's immigration system is shored up -- is refusing to bring the Senate-passed bill to the floor for a vote.

"The most urgent national security threat facing the American people right now is the possibility that Congress abandons Ukraine and allows Vladimir Putin's Russia to win," said Democratic Minority Leader Hakeem Jeffries.