DAMASCUS  - Syria has proposed Cairo, Vienna and Geneva as venues for U.N. investigators to question six Syrian officials in a probe into the killing of a former Lebanese prime minister, a Syrian official said on Saturday.

The U.N. investigating team led by German prosecutor Detlev Mehlis had requested to interview the Syrian officials in the Lebanese capital, Beirut, where former Lebanese Prime Minister Rafik al-Hariri was killed in a bomb blast in February.

The U.N. investigation has implicated senior Syrian and Lebanese officials in Hariri's killing. The six that Mehlis's team want to interview include Syrian President Bashar al-Assad's powerful brother-in-law and military security chief, Major General Assef Shawkat.

"Syria has proposed several venues for the meetings ... Cairo, Vienna and Geneva. President Bashar al-Assad has said Syria will cooperate with the international investigation," the official told Reuters, without giving further details.

In a defiant speech on Thursday, Assad reiterated his country had no role in the killing and said it would cooperate with the probe but not at the expense of its national interests.

U.S. President George W. Bush called on Syria on Friday to cooperate fully with the U.N. inquiry and criticised Assad for delivering "a strident speech" that attacked both the Lebanese government and the integrity of Mehlis.

Anti-Syrian sentiment is still running high in Lebanon where many accused Damascus and its Lebanese allies of killing Hariri.

U.N investigators questioned Lebanese President Emile Lahoud, a staunch ally of Damascus, on Friday as part of their inquiry.

According to their investigation, one of the suspects had contacted Lahoud shortly before the bombing that killed Hariri and 22 others near Beirut's seafront.

Lahoud has denied he had the conversation.

The U.N. report, which did not refer to Lahoud as a suspect, in October prompted a unanimous Security Council resolution threatening Damascus with unspecified action if it did not cooperate with Mehlis's inquiry.

Hariri's assassination sparked mass protests in Beirut that forced Syria to bow to world pressure and end its 29-year military presence in Lebanon in April. (Reuters)