President Obama told congressional leaders Tuesday that he has the authority he needs to take on the Islamic State of Iraq and Syria (ISIS, also known as ISIL), according to the White House.

The president met with House Speaker John Boehner, R-Ohio, House Minority Leader Nancy Pelosi, D-Nev., Senate Majority Leader Harry Reid, D-Nev., and Senate Minority Leader Mitch McConnell, R-Ky., ahead of a speech to the nation on his plan to deal with the Islamic militant group planned for Wednesday night.

"The president told the leaders that he has the authority he needs to take action against ISIL in accordance with the mission he will lay out in his address tomorrow night. He reiterated his belief that the nation is stronger and our efforts more effective when the President and Congress work together to combat a national security threat like ISIL," the White House said in a statement.

Mr. Obama also told the leaders he would welcome actions by Congress "that would aid the overall effort and demonstrate to the world that the United States is united in defeating the threat," the statement said.

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The leaders did not speak with reporters outside the White House after the meeting and offered scant details on what the president told them. Reid merely said the president gave a preview of the speech that everyone would hear Wednesday night. Pelosi said the session offered a"valuable opportunity for consultation on advancing security and stability in the region and beyond."

Boehner offered slightly more detail about what kind of strategy he would support in a statement issued by an aide after the meeting. He urged the president to act quickly, to avoid a complex situation made worse by delay as it was in Syria, and said he would back the use of U.S. troops to help advise the Iraqi Security Forces or to assist with the lethal targeting of ISIS leadership. He also expressed support for training and equipping the Syrian opposition.

He also said the administration should re-examine border and homeland policies to ensure there are no loopholes or weaknesses ISIS could use to carry out an attack.

On the Senate floor Wednesday morning, McConnell said the president, "needs to present this plan to Congress and the American people and where the president believes he lacks authority to execute such a strategy, he needs to explain to Congress how additional authority for the use of force will protect America."

Unlike Boehner, McConnell said that he believes the president should seek congressional authorization "whether or not he may think he's authorized to do what he intends to do."

"I think the view of myself and most of my members is the president should be seeking Congressional approval, period, for whatever he decides to do because that's the way you hear from those of us who represent everyone in the country, that's the way you get congressional support," McConnell told reporters Tuesday afternoon.

Mr. Obama has indicated he believes he has the authority he needs in the region without turning to Congress, although lawmakers are increasingly suggesting they should have a voice in the matter.

Sen. Bill Nelson, D-Florida, a senior member of the Senate Armed Services Committee, and Rep. Frank Wolf, R-Virginia, have introduced legislation that would authorize the use of U.S. military force against ISIS.

"Congress has to participate," Wolf said. "It isn't enough to stand on the sidelines."

But others say it's unlikely to happen. House Armed Services Committee Chairman Buck McKeon, R-California, said that "as a practical matter" he's not sure there's time for a full debate and a vote. Plus, he said, some lawmakers won't want to vote on the issue.

He said he expects congressional leadership to decide that issue.

A Washington Post-ABC News poll out Tuesday shows that 71 percent of Americans support airstrikes in Iraq, a sharp increase from 54 percent three weeks ago and 45 percent in June. Those numbers rise even higher when only those who believe Obama is too cautious are surveyed: more than eight in 10 support strikes.

Ask Americans who say the president's foreign policy is about right and two thirds, or 66 percent, support strikes.

When the location of the airstrikes shifts to Syria, 65 percent of Americans say they would support that move. Though lower than the level of support for strikes in Iraq, it is more than double the figure that backed military action in Syria one year ago when the president advocated it as a way to punish President Bashar Assad for using chemical weapons on his own people.

The White House has offered few details about Mr. Obama's Wednesday speech except to suggest that previous U.S. counterterrorism operations "are a relevant reference point" for how the president might approach ISIS now.

On Tuesday, White House spokesman Josh Earnest said the speech will focus on the "next phase" of the fight against ISIS.

"Generally speaking, at the core of that next phase is understanding and protecting the core national security interests of the United States and protecting the American people. So there are a couple different ways in which the president will talk about this," he told reporters.

Some lawmakers say that's not enough.

"It looks like nothing much new that kind of continuing the same counterterrorism strategy that we've been following the last five years and that has not been able to stop [ISIS]," said McKeon."In fact they've grown stronger, so that's something that's very bothersome."

"I don't get the feeling of urgency from the president that I got while we were over in the Middle East. While the president waits to come up with a strategy ISIS is growing stronger day by day," he added.