WASHINGTON (AP) — As a U.S. senator from Illinois running for the White House in 2007, Barack Obama sponsored a resolution to prohibit President George W. Bush's administration from taking military action against Iran unless it was explicitly authorized by Congress. His idea died in committee.

Nearly seven years later, U.S. fighter jets and unmanned drones armed with missiles have conducted under Obama's orders more than 150 airstrikes against the Islamic State group over the past five weeks in Iraq even as the White House has yet to formally ask Congress for authorization for the expanding air campaign.

Obama said in his address to the nation Wednesday that he had authorized U.S. airstrikes inside Syria for the first time, along with expanded strikes in Iraq, as part of "a steady, relentless effort" to root out Islamic State extremists. He did not say how long he expected the fighting to last.

The White House says Bush-era congressional authorizations for the war on al-Qaida and the Iraq invasion give Obama the authority to expand the fighting in Syria and Iraq without new approval by Congress under the 1973 War Powers Act. That law, passed at the height of the Vietnam War, serves as a constitutional check on the president's power to declare war without congressional consent. It requires presidents to notify Congress within 48 hours of military action and limits the use of military forces to no more than 60 days unless Congress authorizes force or declares war.

The administration's tightly crafted legal strategy has short-circuited the congressional oversight that Obama once championed. The White House's use of old authorizations as grounds for the growing air war has generated a chorus of criticism that the justifications are, at best, a legal stretch.

White House spokesman Josh Earnest on Thursday cited the 2001 military authorization Congress gave Bush to attack any countries, groups or people who planned, authorized, committed or aided the Sept. 11, 2001, terrorist attacks. Earnest described the 2001 Authorization for Use of Military Force, generally known as the AUMF, as one that Obama "believes continues to apply to this terrorist organization that is operating in Iraq and Syria."

The Islamic State group, which was founded in 2004, has not been linked to the 9/11 attacks, although its founders later pledged allegiance to Osama bin Laden. In February, al-Qaida declared that the Islamic State group was no longer formally part of the terror organization. And in recent weeks, senior U.S. officials, including Homeland Security Secretary Jeh Johnson and Matthew Olsen, head of the National Counterterrorism Center, have drawn significant distinctions between al-Qaida and the Islamic State group.

Earnest said Thursday that Obama welcomes support from Congress but that it wasn't necessary. "The president has the authority, the statutory authority that he needs," Earnest said.

Others disagreed.

"I actually think the 2001 AUMF argument is pretty tortured," said Rep. Jim Himes, D-Conn., who serves on the House Intelligence Committee. "They are essentially saying that ISIL is associated with al-Qaida, and that's not obvious," Himes said, using an alternate acronym for the Islamic State group. "Stretching it like this has dangerous implications."

Himes supports a new congressional vote, as does another Democrat on the Intelligence Committee, Rep. Adam Schiff of California.

An unlikely critic of the president relying on the 2001 order is Jack Goldsmith, head of the Justice Department's Office of Legal Counsel under President George W. Bush and a legal architect of the Bush administration's war on terror. Goldsmith said in the Lawfare blog that "it seems a stretch" to connect the Islamic State group to al-Qaida, considering recent rivalry between the two groups.

The White House also finds authorization under the 2002 resolution that approved the invasion of Iraq to identify and destroy weapons of mass destruction. That resolution also cited the threat from al-Qaida, which Congress said then was operating inside Iraq. But the U.S. later concluded there were no ties between al-Qaida and Iraqi President Saddam Hussein or his government, and the group formally known as al-Qaida in Iraq — which later evolved into the Islamic State group — didn't form until 2004, after the U.S.-led invasion.

Obama uses both authorizations as authority to act even though he publicly sought their repeal last year. In a key national security address at the National Defense University in May 2013, Obama said he wanted to scrap the 2001 order because "we may be drawn into more wars we don't need to fight." Two months later, Obama's national security adviser, Susan Rice, asked House Speaker John Boehner to consider repealing the 2002 Iraq resolution, calling the document "outdated."

Obama himself said Wednesday that he wants congressional backing, not for U.S. airstrikes but for the buildup of American advisers and equipment to aid Syrian opposition forces. House Republicans spurned a vote on that separate request earlier this week, but House Speaker John Boehner is now siding with the administration. The White House acknowledged that it could not overtly train Syrian rebels without Congress approving the cost of about $500 million.

"Committing American lives to war is such a serious question it should not be left to one person to decide, even if it's the president," said former Illinois Rep. Paul Findley, 92, who helped write the War Powers Act.

Since U.S. military advisers went into Iraq in June, the administration has maneuvered repeatedly to avoid coming into conflict with the War Powers provision that imposes a 60-day time limit on unapproved military action. Seven times, before each 60-day limit has expired, Obama has sent new notification letters to Congress restarting the clock and providing new extensions without invoking congressional approval. The most recent four notifications have covered the airstrikes against the Islamic State group that began Aug. 8.

An international law expert at Temple University's Beasley School of Law, Peter J. Spiro, described the letters as workarounds that avoided the controversy over U.S. bombing in 2011 in Libya. Obama said Libya didn't require congressional permission because the fighting there was not sustained and there were no active exchanges of fire with hostile forces. The seven recent notification letters, Spiro said, amount to "killing the War Powers Act with 1,000 tiny cuts."

Former Sen. Richard Lugar, R-Ind., who now heads the Lugar Center for foreign affairs in Washington, said Obama could ask for congressional approval in a way that would be less formal than a specific war resolution — perhaps either as an appropriations request or a simple resolution.

"It may not be the most satisfactory way to declare war," Lugar said. "But it may be a pragmatic compromise for the moment."

___