U.S. counter-terrorism aide due in Libya on Tuesday: source

The U.S. Consulate in Benghazi is seen in flames during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012.

TRIPOLI (Reuters) - The top U.S. counter-terrorism adviser will visit Libya on Tuesday to discuss the investigation into the killing of the U.S. ambassador at the U.S. consulate in Benghazi last month, a Libyan protocol official said.

John Brennan, the senior White House adviser on counter-terrorism, will meet with the president of the national congress, Mohammed Magarief, as well as army, intelligence, interior and foreign ministry officials, said the official, who declined to be named.

U.S. ambassador Chris Stevens was killed along with three other Americans on September 11 in an attack on the consulate in Benghazi.

American FBI agents traveled to the Libyan capital Tripoli a few days after the attack to join in the investigation, but domestic political upheavals and disagreement over the terms of the cooperation held up a visit to Benghazi for over two weeks.

Attempts to form Libya's first democratic government were set back on Monday when prime minister-elect Mustafa Abushagur received a vote of no confidence in the congress, the embryonic parliament, after his cabinet failed to secure majority approval.

Libya desperately needs a viable government so that it can strengthen law and order and focus on reconstruction and on healing regional divisions opened up by the war that toppled long-time dictator Muammar Gaddafi last year.

(Reporting by Hadeel al-Shalchi; Editing by Kevin Liffey)