The official, who asked not to be named, said the ministry's legal adviser Riad al-Daoudi had met in the Lebanese capital last week with Detlev Mehlis, who is trying to find the killers of former Lebanese Prime Minister Rafik al-Hariri.

But the official said the German prosecutor had refused to discuss Syria's concerns about where its officials should be questioned and had ignored its counter-proposals.

"Mr Mehlis was rigid and did not pay any attention to the issues raised by Mr Riad al-Daoudi," the official said. "Mr Daoudi visited Beirut on an unofficial mission to touch base with Mr Mehlis on the details of his request."

Mehlis's team wants to interview the Syrian officials, said by Lebanese political sources to include the brother-in-law of President Bashar al-Assad, at its headquarters near Beirut.

Daoudi told Mehlis Syria felt this could cause internal problems in Lebanon and affect Syrian-Lebanese relations, the official said. Daoudi had also proposed that the U.N. team choose a venue in Damascus for the questioning, or hold it at Arab League headquarters in Cairo, he added.

"Mehlis refused to discuss this issue. None of the issues that (Daoudi) raised were agreed upon," the official said.

U.N. officials could not immediately be reached for comment.

Anti-Syrian sentiment is still running high in Lebanon where many people say Damascus and its Lebanese allies were behind the February 14 bombing that killed Hariri and 22 others in Beirut.

However, Syria retains the support of some political groups in Lebanon, especially the Shi'ite Amal and Hizbollah factions.

In a fiery speech on Thursday, President Assad reiterated that his country had no role in Hariri's killing.

He said Syria would cooperate with the U.N. investigation, but not at the expense of its national interests.

In an interim report last month, Mehlis said he had evidence of Syrian and Lebanese involvement in Hariri's assassination.

A Security Council resolution demands that Syria cooperate fully with the U.N. inquiry or face unspecified action.  (Reuters)