A United Nations report accusing senior Syrians of complicity in the murder in February of Rafik Hariri, a former Lebanese prime minister, has caused diplomatic dilemmas for President George W Bush and Bashar Assad, the Syrian president.

American, British and Israeli intelligence agencies have concluded that Assad’s position has been seriously weakened by the allegations that his powerful brother-in-law, Asef Shawkat, the head of Syria’s military intelligence, plotted to murder Hariri, a prominent opponent of Syrian involvement in Lebanon, who died when his motorcade was blown up in Beirut.

US officials were publicly adamant last week that the UN should consider punitive action against Syria. But there was private concern in Washington that Assad might fall before a viable alternative regime emerged. “We don’t want chaos in Syria while we’re trying to stop chaos in Iraq,” an official said.

According to senior Middle East sources, Assad was present at a meeting when Shawkat and the president’s brother, Maher, argued that Hariri should be assassinated. Assad is said to have rejected the plan, but Shawkat and Maher — who is also chief of the presidential guard — allegedly went ahead anyway.

The naming of both men in the UN report by Detlev Mehlis, the German prosecutor assigned to investigate the case, has placed Assad in a difficult position.

He must either brazen out the allegations and ignore international pressure for a trial — or he must order the arrest of the man who provides his regime with its security backbone.

Regional intelligence sources have described the exposure of the Syrian plot as the greatest threat to the Assad family’s hegemony in Syria since Bashar inherited the presidency from his father, Hafez, five years ago.

Washington’s concern is that he has no obvious successor and a chaotic power struggle could serve the interests of Iraqi insurgents who have been using Syria as a base.

Military retaliation has been publicly ruled out.

The UN security council will meet on Tuesday to discuss the report, but Mehlis has already been given until December 15 to continue his investigation.

Explore World News

• Iraq News

• US & Americas News

• Europe News

• Middle East News

• Asia News

• Africa News

• Ireland News

Times Recommends

• Congo's rangers risk their lives to guard gorillas
• Pearl farming in China losing its lustre
• Axl Rose mystery as album arrives at last