Syria agreed to let the top U.N. relief official and newly designated U.N.-Arab League envoy Kofi Annan visit, but widened its crackdown to other restive areas. Valerie Amos, the U.N. undersecretary-general for humanitarian affairs and emergency relief, said the regime of President Bashar Assad gave her permission to visit Syria for three days starting Wednesday. The regime had refused for a month to let Amos visit. She said she intended \"to urge all sides to allow unhindered access for humanitarian relief workers so they can evacuate the wounded and deliver essential supplies.\" The International Committee of the Red Cross -- the only relief agency permitted in Syria -- said Monday a Red Cross and Syrian Arab Red Crescent convoy arrived in the hard-hit central-western city of Homs. It was helping two areas of the city, but was prevented by Syrian troops from entering the devastated Baba Amr neighborhood, held by rebels for several months before regime forces drove them out Thursday after nearly four weeks of relentless shelling, the ICRC said. Troops loyal to the Assad regime have sealed Baba Amr, citing security problems. Amos said she planned to leave the Syrian capital, Damascus, Friday. Her visit was to be followed Saturday by Annan, a former U.N. secretary-general appointed last week as a special representative to Syria for the United Nations and the Arab League. Annan -- secretary-general from 1997 to 2006 and a Nobel Peace laureate with the United Nations in 2001 -- said he intended \"to seek an urgent end to all violence and human-rights violations, and to initiate the effort to promote a peaceful solution to the Syrian crisis.\" Syria \"welcomes\" Annan\'s visit, the state-run Syrian Arab News Agency said. At the same time, Syrian security forces widened their brutal campaign to crush opposition, activists said. Troops fought army defectors in Daraa, a southwestern city 62 miles south of Damascus, activists said. Daraa is where the anti-regime protests began a year ago and was the first city besieged by Syrian forces. The siege of Daraa -- with tanks, soldiers and rooftop snipers -- killed more than 100 people from April 25 through May 5, activists said. Water, power and phone lines were cut. Activists said they feared a similar Daraa siege, if not a worse one, was about to take place. Syrian forces also bombarded the western-central city of Rastan, 12 miles north of Homs, Monday, activists said. Rastan was bombarded by Syrian tanks and helicopters Sept. 27 through Oct. 2 in an intense fight with opposition forces that left at least 27 people dead. With the crackdown expanding, U.S. Sen. John McCain, R-Ariz., called on the United States Monday to conduct an extensive air bombardment of Syrian targets, with Arab League permission, to protect anti-government fighters and civilians. McCain, an early advocate of armed intervention in Libya, said in a speech on the Senate floor that if Assad retained power in defiance of world pressure to leave office, the United States would suffer a \"strategic and moral defeat.\" Assad has consistently rejected criticism of his tactics and vowed to crush protesters, who he describes as terrorist gangs financed by hostile foreign powers. His attempts to defeat them escalated sharply last month, after an Arab League peace proposal to the U.N. Security Council that called on him to step aside was vetoed by Russia and China. U.N. General Assembly President Nassir Abdulaziz al-Nasser condemned the vetoes and called for the Security Council veto to be abolished. He told the British newspaper The Independent Monday the power of a U.N. state to unilaterally stop the enactment of legislation was no longer defensible and a danger to world peace and security.