"I can't imagine saying something like the assassination of ambassadors is a bump in the road, when you look at the entire context, the assassination, the Muslim Brotherhood president being elected in Egypt, 20,000 people killed in Syria, Iran close to becoming a nuclear nation, that these are far from being bumps in the road," he told ABC.
"They represent events that are spinning out of the kind of influence we'd like to have. We're at the mercy of events rather than shaping the events in the Middle East."
U.S. officials are investigating the deaths in Libya, which occurred when the consulate was breached.
Obama has said extremists used an anti-Islam video as an excuse to assault U.S. interests overseas, including the incident in Benghazi.
Romney intends to return to the subject of international affairs and discuss foreign aid, trade agreements and international development when he addresses the Clinton Global Initiative in New York on Tuesday, according to a person familiar with the campaign's thinking.
Romney, like Cantor, took a slap Monday at Obama's handling of relations with Israel.
"The president doesn't have time to actually spend time with leaders of these nations, particularly Bibi Netanyahu, I find that very troubling," he said.
In a campaign setting records for television advertising, both campaigns released new commercials during the day.
Obama's latest seeks to extend the controversy that erupted when Romney was seen on video saying that, as a candidate, he doesn't worry about the 47 percent of Americans who he said pay no income tax and see themselves as victims deserving of a wide range of government benefits.
"Maybe instead of attacking others on taxes, he should come clean on his," says the 30-second commercial, airing in battleground Ohio.
Romney last week released his 2011 tax return, showing he paid $1.94 million in federal taxes on income of $13.7 million. The 14.1 percent rate is less that millions of American families pay because Romney's earnings come from capital gains and dividends, which are taxed at a lower rate than wages.
Romney's new ad shows a shuttered factory and says fewer Americans are working these days. It accuses the president of failing to stand up to China in matters of trade, and says the Asian nation steals "American ideas and technology ... everything from computers to fighter jets."
Associated Press writer Philip Elliott contributed from Washington. Espo reported from Washington.
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