Radical anti-U.S. cleric Moqtada al-Sadr warned that any U.S. training mission in Iraq after 2011 would amount to an occupation force and need to be opposed by "military means," in a letter seen on Sunday.

The letter, released on Saturday in the Shiite cleric's base in the shrine city of Najaf, came after Baghdad agreed to open talks with Washington for a training mission post-2011, when all U.S. troops are due to have left.

Turkish Foreign Minister Ahmet Davutoglu will visit Syria on Tuesday with the message that Ankara "has run out of patience" with the ongoing violence, Prime Minister Recep Tayyip Erdogan said.

"We have reached the end of our patience and that's why I am sending the foreign minister to Syria on Tuesday," Erdogan was quoted by the Anatolia news agency as saying.

U.N. leader Ban Ki-moon told Syrian President Bashar Assad on Saturday to immediately end his deadly military campaign against opponents, the United Nations said.

Ban also said the use of mass arrests must also be halted in Syria in the first contacts between the two since April.

Almost a quarter of a million Israelis rallied in central Tel Aviv on Saturday, police said, for a mass protest aimed at pushing the government into reforms to ease the cost of living.

The organizers appeared to have achieved their target of drawing a "critical mass" out onto the streets to underline the staying power of a movement which began in mid-July over housing costs.

Security forces on Saturday arrested prominent opposition figure and former political prisoner Walid al-Bunni and his two sons, Syrian Observatory for Human Rights chief Rami Abdel Rahman said.

The arrests came after Syria vowed on Saturday to hold "free and transparent" elections by the end of 2011 as Arab states in the Gulf joined a chorus of Western pressure over its deadly suppression of anti-regime protests.

Rebel commanders said their fighters captured the town of Bir Ghanam, 80 kilometers south of the Libyan capital, on Saturday.

An Agence France Presse correspondent, although he did not visit Bir Ghanam, was with the several hundred fighters as they advanced north on a road strewn with burned-out vehicles of the Libyan army, some with bodies of dead soldiers inside.

Foreign Minister Walid Muallem said on Saturday that elections to a new parliament will be held by year's end, as Syria's regime faces international pressure over its deadly crackdown on protests.

"Syria will hold free and transparent elections that will give birth to a parliament representing the aspirations of the Syrian people," Muallem said in a meeting with foreign ambassadors posted to Damascus.

Syria's President Bashar Assad has no future in politics, German Foreign Minister Guido Westerwelle said in an interview to be published Sunday.

"I don't believe that Assad has a political future ahead of him which is supported by the Syrian people", Westerwelle told the German Sunday newspaper Allgemeine Sonntagszeitung.

Gulf Arab states on Saturday turned up the heat on Damascus, joining a growing chorus of pressure after Syrian security forces shot dead at least 22 people as tens of thousands staged anti-regime protests.

The six-member Gulf Cooperation Council called for an "immediate end to violence... and bloodshed."

The State Department on Friday urged Americans in Syria to leave the country immediately and advised those who remain in the country to restrict their movements, as the Syrian government intensified a violent crackdown on opposition protesters.

The warning came as congressional calls grew for the Obama administration to impose severe new sanctions on President Bashar Assad's regime.