BENGHAZI, Libya - The top U.S. diplomat for the Middle East says President Barack Obama has invited the Libyan rebels' National Transitional Council to open an office in Washington D.C., but he stopped short of formal recognition.

Tuesday's statement by Jeffrey Feltman comes hours after NATO launched its most intense bombardment yet against Moammar Gadhafi's stronghold of Tripoli.

Feltman told reporters in the eastern city of Benghazi that he expects Congress to vote soon to let frozen regime assets in the U.S. be used for purely humanitarian aid in Libya.

He says the Americans aren't negotiating with Gadhafi and the opposition council is considered the legitimate representative of the Libyan people. But he did not offer it formal recognition, as other countries have done.