Syrian Foreign Minister Walid Moallem said that his country may resort to more "painful" measures if the United States doesn't give an official explanation for a deadly cross-border raid. Syria retaliated to the October 26 US raid that it says killed eight people by ordering the closure of an American school and cultural center in Damascus, but Moallem said that those measures were "introductory." Speaking on Sunday in a TV interview with the Lebanese ANB satellite station, he warned Syria could escalate its response in the future, but did not elaborate. Last Thursday, tens of thousands of Syrians poured out onto a Damascus square in a government-orchestrated rally to denounce the US raid. A high ranking government official also challenged Washington to prove that US helicopters had targeted a top al-Qaida terrorist in the attack which Damascus says killed eight civilians.