BEIRUT, Feb 25: A UN team vowed impartiality on Friday in probing the murder of ex-premier Rafik Hariri, as Lebanon waited for powerful neighbour Syria to begin a promised troop redeployment.

A day after Lebanese Defence Minister Abdel Rahim Mrad announced an imminent pullback of Syrian troops to the eastern Bekaa Valley, on the border with Syria, no troop movements on the ground had been seen on Friday.

Damascus is under pressure from abroad and from Lebanon's opposition to withdraw from its smaller neighbour, where it maintains 14,000 troops and dominates the political scene.

Amid that pressure, the Syrian-backed government in Beirut is bracing for a possible parliamentary no-confidence vote on Monday, which could bring to a head a crisis sparked by Hariri's assassination on February 14.

The United States, Europe and the United Nations have put pressure on Syria to pull its troops and an unknown number of secret service agents out of Lebanon following Hariri's killing, which the opposition has blamed on the pro-Syrian regime and Damascus.

The authorities in Beirut have denied any responsibility in the killing and agreed to cooperate with the United Nations commission of inquiry but have rejected a full international probe.

Three senior Irish police officers, who arrived in Lebanon late on Thursday to take part in the investigation at the request of the United Nations, held separate talks with the Lebanese ministers of interior and judicial affairs.

Afterwards, Interior Minister Suleiman Frangieh pledged cooperation while insisting that the Irish officers were "not investigators, but are here to give their opinion."

Justice Minister Adnan Addum said the team was in Lebanon "to collect information ... and they are working within the limits of their prerogatives ... within the scope of Lebanese sovereignty." -AFP