Washington (CNN) President Barack Obama on Wednesday made the case for Congress to formally authorize the use of military force in the war against ISIS, declaring that congressional passage of the measure makes the U.S. "strongest" in the fight, and that "ISIL is going to lose."

"Now, make no mistake, this is a difficult mission and it will remain difficult for some time," he said during an afternoon press conference. But, he added, "Our coalition is on the offensive, ISIL is on the defensive and ISIL is going to lose."

Obama, flanked by Vice President Joe Biden, Secretary of State John Kerry and Secretary of Defense Chuck Hagel, outlined the parameters of the request he delivered to Congress earlier that day. He said the bill reflects "our core objective to destroy ISIL," and includes authority for a "systemic and sustained campaign of airstrikes," support and training for forces on the ground and humanitarian assistance.

He made clear, however, that the Authorization for the Use of Military Force, or AUMF, does not call for the deployment of ground troops in Iraq or Syria.

"I am convinced that the U.S. should not get back into another ground war in the Middle East -- it's not in our national security interest and not necessary for us to defeat ISIL," he said.

The proposal does give the military the "flexibility" to confront "unforeseen circumstances," potentially by deploying special forces in the region.

Lawmakers on Capitol Hill received a draft AUMF, a resolution that would formally authorize the already six-month-old U.S. military effort against the militant group.

The joint resolution would limit the President's authority to wage a military campaign against ISIS to three years and does not authorize "enduring offensive ground combat operations," according to text of the resolution.

In a letter to Congress , Obama explained that the draft resolution would give him the authority to authorize "ground combat operations in limited circumstances," including rescue operations and special forces operations to "take military action against ISIL leadership."

The resolution would also sunset the 2002 AUMF that spawned the Iraq War. Obama withdrew American troops from Iraq in 2011, but the military authorization remains in effect.

The resolution drafted by the White House does not repeal the 2001 military force authorization that has served as the legal justification for the military campaign against ISIS and other U.S. military efforts to combat terrorism around the world.

The document also specifically notes that ISIS poses a "grave threat" to U.S. national security interests and regional stability.

And Obama detailed the ISIS threat in a letter to Congress accompanying the draft legislation.

"The so-called Islamic State of Iraq and the Levant (ISIL) poses a threat to the people and stability of Iraq, Syria, and the broader Middle East, and to U.S. national security," Obama writes. "It threatens American personnel and facilities located in the region and is responsible for the deaths of U.S. citizens"

As in the draft resolution, Obama goes on to name the Americans killed in ISIS captivity, "including James Foley, Steven Sotloff, Abdul-Rahman Peter Kassig, and Kayla Mueller."

There is broad support in Congress for a formal AUMF, though lawmakers disagree on the scope of the military powers that should be handed to the President.

The Hill sounds off

House Republican leaders were quick to dismiss the White House draft authorization as too limited, insisting that the President should have fewer limitations.

"If we are going to defeat this enemy, we need a comprehensive military strategy and a robust authorization, not one that limits our options," House Speaker John Boehner said in a statement Tuesday. "Any authorization for the use of military force must give our military commanders the flexibility and authorities they need to succeed and protect our people...I have concerns that the president's request does not meet this standard."

Boehner's No. 2, Rep. Kevin McCarthy, echoed Boehner's support for an AUMF as well as his criticism of the limits the White House's draft would impose.

"I am prepared to support an Authorization for Use of Military Force (AUMF) that provides new legal authorities to go after ISIL and other terrorist groups. However, I will not support efforts that impose undue restrictions on the U.S. military and make it harder to win," McCarthy said in a statement.

House Democratic Leader Nancy Pelosi took the opposite path during a press conference Wednesday.

"We hope to have bipartisan support for something that would limit the power of the President, but nonetheless protect the American people in a very strong way," Pelosi said.

Pelosi added that she hoped the three-year authorization would be longer than needed to defeat ISIS.

Pelosi also offered her support for repealing the 2002 authorization, another provision included in Obama's draft resolution.

"I don't see any reason -- in fact I actively support -- repealing the 2002 authorization. It was based on a false premise," Pelosi said. "Nonetheless, it should go, and it should go now."

Sen. Rand Paul of Kentucky, who is staffing up for a potential 2016 presidential bid, took the opportunity to slam likely Democratic presidential nominee Hillary Clinton.

"I do really blame Hillary Clinton's war in Libya," Paul said Wednesday on Fox News referring to the NATO campaign to oust Libyan dictator Moammar Gadhafi authorized by Obama while Clinton was secretary of state.

Libya has erupted into civil war and has become a breeding ground for radical Islamic fighters, many of whom have left to join ISIS's ranks.

Paul also said the U.S. needs to supply more weapons to Kurdish fighters fighting ISIS in Iraq, but said the U.S. should refrain from getting involved in the war in Syria -- fearing weapons supplied to moderate fighters could get into ISIS's hands.

Paul has been at odds with his Republican colleagues on many aspects of foreign policy, especially in urging for a more restrained, and not limitless, authority to fight ISIS.

Projecting American unity

Obama urged Congress during his State of the Union address to formally authorize the military campaign to "show the world that we are united in this mission" and Secretary of State John Kerry urged Congress to swiftly pass the resolution.

"We are strongest as a nation when the Administration and Congress work together on issues as significant as the use of military force," Kerry said. "This is a moment where Congress can make it clear all over the world that no matter differences on certain issues, at home we're absolutely united and determined in defeating ISIL."

Obama again noted in his letter to Congress Wednesday that he already has the authority to fight ISIS, "I have repeatedly expressed my commitment to working with the Congress to pass a bipartisan authorization for the use of military force" against ISIS.

Obama also stressed that the White House's draft resolution would constrain the U.S. military effort and would not authorize "long-term, large-scale ground combat operations" like in Iraq and Afghanistan.

While Obama did not repeal the 2001 military authorization, he explained in his letter that he remains "committed to working with Congress and the American people to refine, and ultimately repeal, the 2001 AUMF."