Syria has agreed to allow UN investigators to question its officials over Rafik Hariri's assassination at the United Nations building in Vienna, Syria's deputy foreign minister said Friday. Deputy Foreign Minister Walid Moallem told a news conference that the breakthrough in negotiations with the United Nations came after Syria received "reassurances" that its sovereignty will be respected. A UN commission mandated by the Security Council is investigating the death of former Lebanese Prime Minister Rafik Hariri, who was killed with 20 other people in a massive truck bombing in Beirut on Feb. 14. The commission, headed by German prosecutor Detlev Mehlis, issued an interim report last month that implicated Syrian and Lebanese intelligence services in the assassination. "The (Syrian) leadership has decided to inform Mehlis that it accepts his suggestion, as a compromise, that the venue to listen to the five Syrian officials be the UN headquarters in Vienna," Moallem said. His announcement came a day after Syrian Foreign Minister Farouk al-Sharaa criticized Mehlis for refusing Syrian offers on where and how to question the six Syrian officials that the commission wishes to see. Moallem did not say when the Vienna hearing would take place. He refused to identify the Syrian officials, saying it was a matter of the "secrecy of the investigation." But reports have said they include the brother-in-law of Syrian President Bashar Assad, Brig. Gen. Assef Shawkat who heads Syrian military intelligence. The UN Security Council has told Syria that it has to cooperate fully with the Mehlis commission and warned it of "further action" - diplomatic code for sanctions - if it fails to do so. The killing of Hariri was a watershed in Syria's relations with its western neighbor, Lebanon. It provoked mass demonstrations in Lebanon calling for the withdrawal of Syrian troops, who had been stationed in the country since the second year of the 1975-90 civil war. It also heightened the international pressure for a Syrian withdrawal. Syria withdrew its troops at the end of April, and in the May-June elections, Lebanon elected its first parliament in many years that did not have a pro-Syrian majority.