The new assessment, dated Thursday, said that intelligence agencies remain concerned that al-Qaida and its affiliates are committed to carrying out attacks on Western targets.
But the assessment, obtained by The Associated Press, said there was no information pointing to any known plot.
The bulletin made no mention of Syria, even as President Barack Obama sought congressional approval to use military force against the Syrian government.
The terror threat to the US is different than it was 12 years ago. In 2001, there was credible intelligence about a terror plot, but that information wasn't shared with the right people. Today, the threat is more diffuse. Cyberattacks threaten to disrupt major US operations in the government and the private sector. Lone actors represent another threat - one or two people who are not directly affiliated with al-Qaida but who subscribe to the terror group's ideology and want to strike out because they disagree with US policies.
Iraqi officials and militant groups have said that Iranian-backed Shiite militias are threatening to retaliate against American interests inside Iraq if the US goes ahead with strikes, as Tehran is a close ally of Assad.
The FBI has been reviewing old case files involving Hezbollah and Iran's Quds Force, reaching out to its sources to see whether they know anything new, a law enforcement official said.
