Republican presidential candidate Mitt Romney delivered a sweeping critique on Monday of President Barack Obama's handling of threats in the Middle East, saying Obama's lack of leadership had made the volatile region more dangerous.

In what his campaign called a major foreign policy address, Romney called for a more assertive use of American influence in the Middle East, Europe, Asia and Latin America.

Romney, speaking before the white-uniformed cadets at Virginia Military Institute, questioned Obama's handling of the episode in Libya last month in which US Ambassador Chris Stevens and three other Americans were killed after the US consulate in Benghazi came under militant attack.

The former Massachusetts governor also accused Obama of failing to use US diplomacy to shape events in Iran, Iraq, Israel, Syria, Russia and elsewhere.

"The president is fond of saying that, 'The tide of war is receding,'" Romney said. "And I want to believe him as much as anyone. But when we look at the Middle East today... it is clear that the risk of conflict in the region is higher now than when the president took office."