(CBS/AP) BEIRUT - Syria's most prominent defector has put himself forward as someone to unite the fractured opposition as the disparate factions gathered in Qatar Thursday to try to agree on a transitional leadership if Bashar Assad's regime is toppled.
In the commercial capital of Aleppo, activists said regime forces have intensified their firepower against a rebel challenge over the past two days, with attack helicopters and fighter jets strafing opposition targets as well as artillery bombardments of several neighborhoods. The fighting in Syria's largest city stretched into a sixth day amid expectations of a major government ground assault.
CBS News correspondent Elizabeth Palmer reports that Syrian helicopters flew over Aleppo on Wednesday, but according to activists, they were not shooting - just spotting the positions of rebel fighters on the ground for the next assault.
A rebel Free Syrian Army commander made a bold claim on Wednesday, saying his forces had "captured half the city."
The question, says Palmer, is how long can they hold onto these neighborhoods. The rebels are equipped for street-by-street fighting, guerrilla-style, but they're no match for air power or the regime's heavy artillery.
Brig. Gen. Manaf Tlass, a former close confidant of President Assad, defected in early July and is now in Saudi Arabia, where he told the Al-Sharq Al-Awsat daily that he does not see a future for Syria with his former friend at the helm.
"I will try and help as much as I can to unite all the honorable people inside and outside Syria to put together a roadmap to get us out of this crisis, whether there is a role for me or not," he said.
Tlass, whose father was once defense minister and comes from a prominent Sunni Muslim family, said there were many good people in the regime without blood on their hands and the country's institutions should be preserved. He said he was against the harsh crackdown on the uprising, which began as peaceful protests in March 2011 but morphed into a civil war after a bloody crackdown by Assad loyalists.
He said he had been unable to keep Assad from listening to his close circle of security advisers who counseled him against crushing the opposition.
"Sometimes in a friendship you advise a friend many times, and then you discover that you aren't having any impact, so you decide to distance yourself," he said, explaining that he defected when he realized there was no way to deter the regime from its single-minded pursuit of the security option.
The meeting in Doha will focus on forming a transitional administration that could step in as a stopgap government if rebel forces topple Assad. It marks the most comprehensive bid to bring together various Syrian opposition groups and show world leaders a credible alternative to Assad.
The Syrian National Council has acted as the international face of the revolution, but it's been unable to unite all dozens of disparate rebel factions under one banner or even assert much control over the rag-tag rebel groups fighting inside the country.
Rebels in Aleppo are bracing themselves amid reports that the government is massing reinforcements to retake the embattled city of 3 million, still wracked with clashes.
"Regime forces have been randomly shelling neighborhoods and the civilians are terrified," local activist Mohammed Saeed told The Associated Press via Skype. "The government reinforcements have yet to arrive."
The fighting had spread to neighborhoods close to the center of the city, which has a medieval core that is a UNESCO world heritage site.
Last week, Syrian troops used a similar combination of artillery bombardments and overwhelming ground force to quash the rebel assault on Damascus. Even though the government forces far outgun the rebels, it took them a week to get the assault under control in a sign that the opposition's capabilities are improving.
The White House said Wednesday that the use of heavy weapons in Aleppo showed "the depth of depravity" of Assad's regime. Spokesman Jay Carney said Syrian forces were perpetrating "heinous violence" against civilians in the city.
The Britain-based Syrian Observatory for Human Rights said the fighting and shelling in Aleppo killed 26 people on Wednesday, including many children. It estimated that a total of 160 died throughout the country, where fighting continues in the cities of Hama, Homs, Daraa and Deir al-Zour.
The clashes across the country have made July the bloodiest month so far in the uprising against Assad's regime that began peacefully in March 2011. With death tolls estimated at well over 100 people a day, it has become as bad as Iraq when it was in the depths of a sectarian civil war in 2006. Activists say 19,000 have been killed since the uprising began.
In a visit to Iran Thursday, Syria's deputy prime minister, Omar Ibrahim Ghalawanji, evoked a strong pledge of support from the country's remaining ally in the Middle East, Iran.
"Tehran is ready to give its experience and capabilities to its friend and brother nation of Syria," said Iran's vice president in charge of international affairs, Ali Saeedlou, according to the state news agency. He did not elaborate.