UNITED NATIONS - The lead United Nations investigator into the assassination of Lebanon's former prime minister has delivered his latest report to Secretary-General Kofi Annan, and two UN diplomats said the document was expected to raise new questions about Syria's cooperation.

Detlev Mehlis, who is stepping down from his post but expects his probe to continue, refused to comment Sunday when he met Annan at the UN chief's residence. A previous report in October implicated top Syrian and Lebanese security officials in Rafik Hariri's Feb. 14 assassination and said Damascus must cooperate more with the investigation.

The two UN diplomats, who requested anonymity because Mehlis' latest findings were not yet public, said the new report was expected to question Syria's cooperation again. One of the diplomats said France had prepared a draft UN Security Council resolution, seven paragraphs long, lamenting that there had not been full cooperation. Both stressed that they had not yet read the report.

Such a finding would be important because after Mehlis delivered his earlier report, the council had warned Syria that it would face further action - possibly including sanctions - if it didn't cooperate fully.

Syria denies involvement and has said it is cooperating. At the same time, it has waged a campaign to discredit the commission. Syrian state television has repeatedly broadcast interviews with a Syrian witness, Husam Taher Husam, who recanted his testimony to the commission and said he had been bribed to frame Syria.

Mehlis said Friday he is satisfied with the evidence he has gathered but he would not say if it recommends measures against Syria. He said the commission's findings would not be greatly affected by Husam's retraction.

In an interview broadcast on Russian television on Sunday, Syrian President Bashar Assad again declared his country's innocence and said any attempt to impose sanctions against Syria would destabilize the region.

Last week, members of the Mehlis commission questioned several senior Syrian officials at the UN headquarters in Vienna. UN diplomats there said Rustum Ghazale, the last Syrian intelligence chief in Lebanon who was in charge when Hariri was assassinated, was among them.

In the interview, Assad said that any citizen found guilty of involvement in the murder would be considered a traitor and severely punished, but added that the commission must provide hard proof for its claims.

Mehlis' latest report was expected to be made public on Monday, when it is delivered to the UN Security Council. Mehlis will brief the council on Tuesday, and expects to step down sometime after.

Nonetheless, Lebanon has asked the United Nations to extend Mehlis' commission for six months after its mandate expires on Thursday. The Security Council, whose approval would be required, is likely to agree to extend it until June 15. (AP)