Two top Lebanese security chiefs stepped aside Friday ahead of U.N. international investigation into ex-premier Rafik Hariri's assassination, a move that could meet demands of the opposition and the United Nations (search).

The two commanders said they were putting themselves "at the disposal" of the prime minister, a formula that stops short of outright resigning but means they are stepping aside and will have no executive power.

Maj. Gen. Ali Hajj (search), commander of Internal Security Forces (search), told The Associated Press that he had informed Prime Minister Najib Mikati that "I was placing myself at his disposal in order to facilitate the work of the international investigation commission.

Earlier Friday, Maj. Gen. Jamil Sayyed, director-general of the Interior Ministry's General Security Department, took a similar decision earlier in the day.

The U.N. team was expected to travel to Lebanon in the next few weeks.

The Lebanese opposition has demanded the sacking of five security chiefs and the top prosecutor, accusing them of at least negligence in the Feb. 14 assassination of Hariri in a massive bombing that also killed 20 others. Accusations also involved a coverup as the opposition blamed the Beirut government and its Syrian backers of involvement in the assassination, charges both governments deny.

A U.N. fact-finding mission that spent three weeks in Beirut in March had called for an international investigation and said such probe could not be carried out satisfactorily with the current security chiefs in office.