By Sam Youngman

PORTSMOUTH, New Hampshire (Reuters) - Republican presidential candidate Mitt Romney said on Monday he definitely would have ordered the U.S. military strike that killed al Qaeda leader Osama bin Laden if he had been president.

"Of course," Romney told reporters after a campaign rally. "Even Jimmy Carter would have given that order," he said, invoking the Democratic president during the Iran hostage crisis in 1979-80 and the failed rescue mission he ordered.

President Barack Obama's re-election campaign has questioned whether Romney would have given the order for the U.S. raid in which U.S. forces killed bin Laden at his compound in Pakistan.

Obama's campaign released a video last week spotlighting his decision to approve the raid ahead of the first anniversary of bin Laden's death on Tuesday.

The video featured former President Bill Clinton discussing the responsibility of the commander in chief and included a caption asking: "Which path would Mitt Romney have taken?" Obama adviser Robert Gibbs said on Sunday it was unclear if Romney would have approved the raid.

Republicans have criticized the White House for trying to politicize the death of bin Laden, who had escaped a U.S. manhunt since masterminding the attacks of September 11, 2001. Republican Senator John McCain, who lost the 2008 election to Obama, called it "a cheap political attack."

On Tuesday in New York, Romney will mark the anniversary of bin Laden's killing by appearing with former New York City Mayor Rudy Giuliani and meeting with firefighters.

(Editing by Bill Trott)