The US warned Syria on Tuesday that its president and other top officials should submit to interviews by UN investigators probing the murder of a former Lebanese prime minister. The UN commission set up to investigate the assassination of Lebanese ex-Prime Minister Rafik al-Hariri has asked to meet Syrian President Bashar al-Assad as well as his foreign minister, Farouq al-Shara. âNo one is immune the obligation to provide evidence to a legitimate judicial inquiry,â US Ambassador John Bolton told reporters.He said that Syriaâs ârecord to date has been one of obstructing the investigation, of tampering with the evidence and not making witnesses available in a timely fashionâ. Bolton warned Damascus that the Security Council had made clear it expected âfull and unconditional complianceâ with the UN investigation and that âadditional measures could be taken if need beâ. These actions could include blanket sanctions although such measures are unlikely to get the needed support. They could also include a travel ban and a freeze on assets of anyone who refuses to cooperate. UN investigators want to meet former Vice President Abdel-Halim Khaddam, now living in Paris as soon as possible.