President Obama on Monday defended a campaign ad that suggested Mitt Romney would not have ordered the bin Laden raid, as the president also described the administration's handling of the one-year anniversary as "entirely appropriate." 

Responding to a question at a press conference on whether White House attention to the anniversary might seem like "excessive celebration," Obama said it was not. And he effectively challenged Romney to "explain" himself, after Romney said in 2007 that, "it's not worth moving heaven and earth spending billions of dollars just trying to catch one person." 

Romney now says that "of course" he would have ordered the raid. 

"I'd just recommend that everybody take a look at people's previous statements," Obama said Monday, during a joint press conference with Japanese Prime Minister Yoshihiko Noda. "I assume that people meant what they said when they said it." 

He continued: "I said that I'd go after bin Laden if we had a clear shot at him, and I did. ... If there are others who have said one thing, and now suggest they'd do something else, then I'd go ahead and let them explain it." 

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The topic of bin Laden's death has emerged rapidly as a campaign issue in the evolving general election battle between Obama and Romney. 

Romney said earlier Monday, while speaking to reporters in New Hampshire, that he would have approved the mission. 

"Of course. Even Jimmy Carter would have given that order," Romney said, answering a reporter's question. 

Romney has clarified that 2007 quote before. 

In fact, days after he made the comment to an Associated Press reporter, Romney explained during a 2007 GOP primary debate that he would in fact pursue bin Laden. 

"Of course we get Usama bin Laden and track him wherever he has to go, and make sure he pays for the outrage he exacted upon America," Romney said. 

He added: "He will die." 

The Associated Press contributed to this report.