Syria says it will halt violence by Thursday morning but reserves right to respond to aggression Updated 12:50 PM ET (CBS/AP) BEIRUT - Syria promised to stop fighting in time for Thursday's deadline for a cease-fire brokered by special envoy Kofi Annan but reserved the right to respond to any aggression, a significant hedge against any end in the fighting that has convulsed the nation for more than a year. The statement came Wednesday as Annan was in Tehran to seek support for his faltering plan to stop the country's slide toward civil war. Iran is one of Syria's most powerful allies. Many world leaders see Annan's plan - which called for Syria to pull its tanks back to barracks on Tuesday, followed by a full cease-fire by both sides by 6 a.m. Thursday - as the best hope to calm a year-old conflict that has killed 9,000 people. But the U.S. and others also are skeptical President Bashar Assad's regime will fully comply after several previous failures. Syria disregarded the Tuesday deadline, and was still attacking its opponents Wednesday with rockets and mortar fire. In a statement carried on the state-run SANA news agency, a defense official said Syria's army successfully fought off "armed terrorist groups," which is the term Damascus uses to describe those behind the country's year-old uprising. "A decision has been taken to stop these missions as of the morning of Thursday, April 12, 2012," the unnamed official said, adding: "Our armed forces are ready to repulse any aggression carried out by the armed terrorist groups against civilians or troops." Annan spokesman Ahmad Fawzi said Syrian Foreign Minister Walid Moallem sent a letter with an identical pledge to the joint U.N.-Arab League envoy. Fawzi said Annan will work with the Syrian government on implementation of his six-point plan to end the bloodshed. "The joint special envoy looks forward to the continue support of relevant countries in this regard," Fawzi said. The U.N. has ruled out any military intervention of the type that helped bring down Libya's Muammar Qaddafi, and several rounds of sanctions and other attempts to isolate Assad have done little to stop the bloodshed. The U.N. peace efforts have received a fair amount of criticism. We think it's going to require military action on the ground to get him to leave," U.S. Sen. John McCain told CBS News correspondent Clarissa Ward. The Syrian uprising is among the most explosive of the Arab Spring, and the U.N. estimates 9,000 people have been killed in the conflict since March of last year. The presence of Syrian tanks, along with security forces and snipers, have largely succeeded in preventing protesters from recreating the fervor of Egypt's Tahrir Square, where hundreds of thousands of people camped out in a powerful show of dissent that ultimately drove longtime leader Hosni Mubarak from power. It's not clear how Syria can fully abide by Annan's plan without risking an embarrassing - and potentially dangerous - Tahrir-style sit-in, or losing control over territory that government forces recently recovered from rebels. And despite Syria's pledge, there was more violence Wednesday, underlining doubts about the regime's intentions. The mounting death toll has prompted intense diplomatic efforts, including a last-minute plea by Annan to Tehran for help. "Iran, given its special relations with Syria, can be part of the solution," Annan said during a news conference with Iran's Foreign Minister Ali Akbar Salehi in Tehran. The geopolitical location of Syria is such that any miscalculation and error can have unimaginable consequences. Iran has opposed any foreign intervention in the crisis and Salehi insisted that "change in Syria" should come under the leadership of Assad. In recent weeks, the government has escalated military attacks on opposition strongholds, particularly after the cease-fire timeline was announced at the beginning of April, prompting accusations that Assad was using the peace plan as cover for more violence. On Wednesday, Syrian troops took control of parts of villages and towns near the border with Turkey, in an apparent attempt to widen control as the truce draws close. The Local Coordination Committees, an activist network, said heavy army reinforcements of 30 vehicles, including tanks, took positions around Azaz without giving further details. The LCC also reported shelling of several rebel-held neighborhoods in the central city of Homs. Homs activist Tarek Badrakhan said troops shelled the Rajoub Mall, one of the city's largest, late Tuesday. Badrakhan said the shopping center in the rebel-held neighborhood of Jouret el-Shayah had shops selling clothes, food products and electrical appliances. SANA, meanwhile, said gunmen shot and killed army Brig. Gen. Jamal Khaled in the Damascus suburb of Aqraba on Wednesday morning. In other violence, the Britain-based Syrian Observatory for Human Rights activist group reported clashes in the Barada Valley region on the outskirts of Damascus between troops and army defectors as government forces stormed the area. The Observatory said "tens of army vehicles" were deploying in the southern town of Maaraba.