WASHINGTON — President Barack Obama will address the nation Wednesday night to outline plans for an expanded U.S. effort to confront violent Islamic State militants in Iraq and Syria.

“The president believes this is a high national security priority,” White House spokesman Josh Earnest said.

Ahead of his remarks to the American people, Obama was meeting Tuesday with congressional leaders from both parties. White House officials have said Obama wants “buy-in” for his strategy from lawmakers, but they have not specified what that means or whether the president will seek a formal authorization for military action.

As he headed to the White House meeting, Senate Minority Leader Mitch McConnell, R-Ky., told reporters Obama “should be seeking congressional approval, period, for whatever he decides to do.”

“There’s pretty broad bipartisan support here for dealing with this group of terrorists,” McConnell said.

But some lawmakers say the president has the authority under the Constitution and no new vote is necessary. Others are reluctant to vote weeks before midterm elections.

In his speech, administration officials said, Obama is expected to outline a broader counterterrorism effort to defeat the Islamic State, moving beyond the current limited mission aimed at using airstrikes to safeguard U.S. interests in Iraq and to ease humanitarian crises. The president will also reiterate his call for Congress to pass a $500 million plan to arm and train the Syrian rebels and ask for similar commitments from allies.

Secretary of State John Kerry was traveling to the Middle East Tuesday to discuss those efforts with leaders in Saudi Arabia and Jordan.

House Speaker John Boehner said Tuesday that the militants pose a serious threat that must be dealt with in Iraq, Syria or wherever they exist. He said no decision would be made on whether Congress would vote until Obama laid out his plan, but the chairman of the House Armed Services Committee said it was highly unlikely there would be a vote this month.

“As a practical matter, I don’t really see the time that it would take to really get this out and have a full debate and discuss all the issues,” Rep. Howard “Buck” McKeon, R-Calif., told reporters after a closed-door briefing on national security threats. He said his panel has 62 members and they’d “probably come up with 10 or 30 or 40 different ideas just from those people.”

Senate Majority Leader Harry Reid of Nevada and House Minority Leader Nancy Pelosi of California were to represent Democrats in the meeting with the president.

The U.S. is already launching airstrikes against Islamic State targets in Iraq, action taken at the request of the Iraqi government and without formal authorization from Congress. But the mission the president is expected to announce would be more expansive and could extend into Syria.

The White House said Obama would speak Wednesday at 9 p.m. EDT from the White House.