WASHINGTON (AP) - The State Department concedes security should have been tighter at the U.S. consulate in Libya where four Americans died in an attack in September.

An independent review found that management failures at the State Department resulted in inadequate security. Fallout from the investigation forced the resignations of four State Department officials yesterday.

Testifying today at the first of two congressional hearings, Deputy Secretary of State William Burns said, "We learned some very hard and painful lessons in Benghazi." He told a Senate panel, "We made the mistaken assumption that we wouldn't become a major target."

But some Republicans contend that warning signs were missed, and that the State Department should have asked Congress for money to boost security in Benghazi. Sen. Jim Inhofe ticked off a long list of incidents involving Westerners in the months before the attack.

Burns pointed out that there was no "specific tactical threat," but he added, "We did not do a good enough job in trying to connect the dots."

Earlier, the Democrat who chairs the Senate panel -- and who is expected to be the next secretary of state -- said the department had "clear warning signs" of a deteriorating security situation. John Kerry also faulted Congress for failing to provide enough money to protect embassies worldwide.