The United States and Britain have called for international pressure against Syria after a U.N. report implicated Syrian officials in the killing of former Lebanese Prime Minister Rafik Hariri.

U.S. Secretary of State Condoleezza Rice and British Foreign Secretary Jack Straw made the appeal in a joint interview with British radio on Sunday.

Ms. Rice said a firm response is needed.

The U.N. report also said that Syrian officials gave false testimony to investigators in the case.

Syrian officials have denied the allegations.  And Sunday, a key Syrian political group - National Progressive Front - rejected the U.N. report, saying it was based on testimony from people lacking credibility.

Syria's official news agency reported President Bashar al-Assad sent a message to members of the U.N. Security Council, which is expected to consider sanctions over the killing.

Some information for this report provided by AP, AFP, Reuters.