WASHINGTON (AP) — President Barack Obama on Wednesday asked Congress to authorize military force against the Islamic State group and urged lawmakers to "show the world we are united in our resolve" to counter the direct threat that militants could pose to the United States.

The president elected on a promise to end America's wars wants a joint resolution in response to the swift rise of extremists who are imposing violent rule across Iraq and Syria and have killed U.S. and allied hostages, as seen in graphic videos.

In a letter to lawmakers that accompanies the three-page draft resolution provided to The Associated Press, Obama said the Islamic State "poses a threat to the people and stability of Iraq, Syria and the broader Middle East and to U.S. national security."

Obama's proposal would ban "enduring offensive combat operations." This ambiguous wording is designed to bridge the divide between lawmakers opposed to ground troops and those who say the commander in chief should maintain the option.

Obama said his draft would not authorize long-term, large-scale ground combat operations like those in the past in Iraq and Afghanistan, with local forces instead carrying that responsibility.

He said he wants the flexibility for ground combat operations "in other more limited circumstances." Those include rescue missions, intelligence collection and the use of special operations forces in possible military action against IS leaders.

Obama planned to discuss the issue at the White House on Wednesday afternoon.

In his letter, he listed four American hostages who died in Islamic State custody and said the group, if left unchecked "will pose a threat beyond the Middle East, including to the United States homeland."

Obama's proposal launches an ideological debate over what authorities and limitations the commander in chief should have in pursuit of the extremists, with the shadow of lost American lives hanging over its fate.

Confirmation of the death of 26-year-old humanitarian worker Kayla Mueller on the eve of Obama's proposal added new urgency. Also, costly wars in Iraq and Afghanistan were a caution to some lawmakers against another protracted military campaign.

Obama is offering to limit authorization to three years, extending to the next president the powers and the debate over renewal for what he envisions as a long-range battle.

He is proposing no geographic limitations where U.S. forces could pursue the militants. The authorization covers the Islamic State and "associated persons or forces," defined as those fighting on behalf of or alongside IS "or any closely-related successor entity in hostilities against the United States or its coalition partners."

Obama's resolution would repeal a 2002 authorization for force in Iraq but maintain a 2001 authorization against al-Qaida in Afghanistan. Obama said in his letter to lawmakers his goal is to refine and ultimately repeal that authorization as well.

The silence on the 2001 authorization drew criticism from some Democrats. "It makes little sense to place reasonable boundaries on the executive's war powers against ISIL while leaving them unchecked elsewhere," said Rep. Chris Van Hollen, D-Md., in a statement, using an acronym for the terrorist group.

California Rep. Adam Schiff, the top Democrat on the House intelligence panel, said he was concerned about a lack of limits on geography and the broad definition of associated forces. He wants "more specific limits on the use of ground troops to ensure we do not authorize another major ground war without the president coming to Congress to make the case for one."

Tennessee Sen. Bob Corker, the chairman of the Senate Foreign Relations Committee, pledged to begin "rigorous hearings" on the White House request.

White House press secretary Josh Earnest said the ground troop limitation would allow special operations missions, such as potential raids targeting Islamic State leaders and the failed attempt last summer to rescue Mueller and other hostages held by the group.

"It's impossible to envision every scenario where ground combat troops might be necessary," Earnest said in the White House's first interview laying out its case for the resolution.

"The president believes this sort of strikes the right balance of enforcing what he has indicated is our policy, while preserving the ability to make some adjustments as necessary," Earnest told The Associated Press.

Obama argues the congressional authorizations that President George W. Bush used to justify military action after the Sept. 11 attacks are sufficient for him to deploy more than 2,700 U.S. troops to train and assist Iraqi security forces and conduct airstrikes against targets in Iraq and Syria.

Critics have said Obama is overstepping outdated authorities to target the new threat from militants imposing a violent form of Sharia law in pursuit of the establishment of an Islamic state.

Obama cast the vote as an important message to America's allies and enemies. "I can think of no better way for the Congress to join me in supporting our nation's security than by enacting this legislation, which would show the world we are united in our resolve to counter the threat posed by ISIL," he wrote to lawmakers.

Presidential aides have consulted with lawmakers from both parties ahead of release of the plan in hopes of lining up support, despite the political divisions that have deadlocked Washington in Obama's second term.

In anticipation of debate and attempts to amend the resolution, Earnest called the offer a "starting point for conversations to take place."

Earnest said the language limiting ground troops was designed not just for domestic political considerations, but to take in the viewpoint of leaders in Iraq and members of the U.S.-Arab coalition targeting IS who are uncomfortable with the idea of a large deployment of U.S. forces.

He also said the lack of geographic limitations will allow pursuit of the extremists beyond the borders of Iraq and Syria.

Earnest also argued the three-year window would give the military time to carry out its strategy before Congress starts debating a renewal.

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(Photo: AP Photo/Evan Vucci)