WASHINGTON — U.S. National Security Advisor Jake Sullivan plans to meet with a group of senior members of Congress after one top Republican warned publicly of an unspecified “serious national security threat.”

Sullivan said he would sit down Thursday with the House contingent of the so-called Gang of Eight congressional leaders. The meeting was scheduled before House Intelligence Committee Chairman Mike Turner on Wednesday issued a cryptic public statement.

The Ohio Republican called on President Joe Biden to declassify “all information relating to this threat.” Turner did not offer further details about the nature of the threat. The matter is related to Russia, according to one person familiar with the matter, who did not provide additional information.

Turner’s decision to go public with the issue, without fully describing it, caused concern in Washington. The incident comes at a time when wars in Ukraine, Israel and Gaza are weighing heavily on the U.S.

House Speaker Mike Johnson sought to calm fears that Americans could face imminent danger, telling reporters there is “no need for public alarm.” He nonetheless said he would “will press the administration to take appropriate action” in the meeting with Sullivan.

Sullivan told reporters at the White House Wednesday he had proactively reached out to the Gang of Eight to set a meeting — which he described a “highly unusual” move. The four House members of that group will meet Sullivan on Thursday, he said.

“That’s been on the books, so I am a bit surprised that Congressman Turner came out publicly today,” Sullivan said at the White House. “That’s his choice to do that. All I can tell you is I’m focused on going to see him.”

House Minority Leader Hakeem Jeffries said he hoped more information on the classified matter would be made public soon. Turner said the committee has provided members with all available material.

The House Intelligence panel’s top Democrat, Jim Himes, also urged calm. “People should not panic,” he said, describing the matter as a longstanding, albeit serious issue.

Sullivan declined to specify the subject of Thursday’s meeting or respond to Turner’s characterization of the national security matter. “I’m not in a position to say anything further today,” he said.

Jeffries, speaking at the Capitol on Wednesday, said “it’s possible” he’ll attend a meeting Thursday. “I’ve got some familiarity with the situation,” he said.

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(—With assistance from Akayla Gardner and Roxana Tiron.)