Mitt Romney led a chorus of Republican criticism of Barack Obama's foreign policy, accusing the President of reducing the killing of the US ambassador to Libya as a mere "bump in the road" rather than part of a chain of events that threatened American interests.
White House press secretary Jay Carney called the accusations "desperate and offensive" and an attempt by the Republican presidential candidate and his allies to gain political advantage in the latter stages of a close race that seems to be trending the President's way.
President Obama flew from the White House to New York, where he will speak to world leaders at the opening of the annual session of the United Nations General Assembly.
The foreign policy spat occurred as Mr Romney said he was shifting to a more energetic schedule of public campaign events, bidding to reverse recent erosion in battleground state polls.
While national polls make the race exceedingly close, Mr Obama has gained ground on Mr Romney in many recent surveys when potential voters are asked to compare the rivals' ability to fix the economy. Sluggish growth and national unemployment of 8.1% make the economy by far the dominant issue in the race.
The same polls show Mr Obama with a healthy lead over Mr Romney when voters are asked which candidate is better equipped to handle foreign policy, and the President has not shied away from trumpeting his decision to order the secret mission by US forces that killed terrorism mastermind Osama bin Laden in his Pakistani hideout more than a year ago.
At the same time, Mr Romney's advisers say voters are more inclined to question Mr Obama's handling of foreign policy after the attack on the US consulate in Benghazi, Libya, earlier this month resulted in the death of US ambassador Chris Stevens and three other Americans.
In an interview with CBS' 60 Minutes at the weekend, Mr Obama was asked if recent events in the Middle East gave him pause for supporting governments that came to power following a wave of regime changes known as the Arab Spring.
Mr Obama said he had long noted that events were going to be rocky, adding that the question itself "presumes that somehow we could have stopped this wave of change". "I think it was absolutely the right thing for us to align ourselves with democracy, universal rights. ... But I was pretty certain and continue to be pretty certain that there are going to be bumps in the road," he said. "There are strains of extremism, and anti-Americans, and anti-Western sentiments and you know can be tapped into by demagogues."
Mr Romney was eager to talk about the topic, squeezing interviews with three TV networks into his schedule and touching on the subject at the beginning of a rally in Colorado - one of several states that could swing either way in the November election. The US President is not chosen by popular vote but by state-by-state elections, making states that do not reliably vote Democrat or Republican important in such a tight race.