U.S. President Barack Obama sent Congress a proposal on Wednesday for authorization to use military force against Islamic State that would limit the operation to three years and bar any large-scale invasion by U.S. ground troops.

But the proposal faced swift resistance from Obama's fellow Democrats wary of another Middle East war and from Republicans who criticize Obama's foreign policy as too passive and want stronger measures against the militants, also known as ISIL.

"I have directed a comprehensive and sustained strategy to degrade and defeat ISIL," Obama wrote in a letter to Congress calling on lawmakers to back his proposal to "show the world we are united in our resolve to counter the threat posed by ISIL."

Obama's plan must be approved by both the U.S. Senate and House of Representatives. Lawmakers said they would begin hearings quickly. Senate Republicans were to meet on the issue later on Wednesday. Some predicted a vote in March.

Islamic State militants have killed thousands while seizing territory in Iraq and Syria in an attempt to establish a hub of jihadism in the heart of the Arab world.

Republicans, who control Congress after November elections, criticized aspects of Obama's proposal, particularly the limits it sets on using ground troops.

The Republican Speaker of the House of Representatives, John Boehner, said the plan would face hearings and debate "and I'm sure changes" in Congress.

"I'm not sure the strategy that has been outlined will accomplish the mission the president says he wants to accomplish," he told reporters after a meeting of Republican House members.

Obama has defended his authority to lead an international coalition against Islamic State since Aug. 8 when U.S. fighter jets began attacking the jihadists in Iraq. But he has faced criticism for failing to seek the backing of Congress, where some accused him of breaching his constitutional authority.

The White House said Obama would make a statement on his request at 3:30 p.m. (2030 GMT).

Using local forces

The plan does not authorize "long-term, large-scale ground combat operations" such as those during the Iraq and Afghanistan wars. Obama said those operations would be left to local forces.

But it does allow for certain ground combat operations including rescue operations or the use of special operations forces. And it allows for the use of U.S. forces for intelligence collection, targeting operations for drone strikes and planning and other assistance to local forces.

Representative Adam Schiff, the top Democrat on the House Intelligence Committee, said Obama's proposal contained too few controls. He said a new authorization should place more specific limits on the use of ground troops and expressed concerns that Obama's plan did not set geographic limits on the campaign.

If passed, the measure would be the first war authorization approved by Congress since lawmakers in 2002 gave then-President George W. Bush authority to wage the Iraq War.

Obama's text includes a repeal of that 2002 measure. But his proposal leaves in place a 2001 authorization, passed shortly after the Sept. 11 attacks, for a campaign against Al-Qaida and its affiliates.

Rights groups urged lawmakers to repeal the 2001 authorization, which did not include an end date and has been invoked by the White House to carry out drone and missile strikes against suspected Al-Qaida militants in Yemen and Somalia.

Obama said he remained committed to working with Congress to "refine, and ultimately repeal" the 2001 AUMF. He said enacting a measure specific to the campaign against Islamic State fighters could serve as a model for revamping the 2001 measure.

Highlights from the request

Authorization for military force would:

— target the Islamic State and associated persons or forces, defined as those fighting with the Islamic State "in hostilities against the United States or its coalition partners;"

— provide no geographic limits on the battle;

— limit ground troops by banning "enduring offensive ground combat operations;"

— expire after three years unless renewed by Congress;

— repeal a 2002 authorization for force in Iraq but maintain a 2001 authorization against Al-Qaida in Afghanistan. Obama says his goal is to refine and ultimately repeal that authorization as well.