Damascus: Syria’s main anti-regime group on Friday accused Washington of undermining the country’s revolution by seeking an opposition overhaul, as rebel forces made important gains in the northwest.

Criticism mounted meanwhile of a video purported to show rebel fighters executing Syrian soldiers, with the UN human rights body saying it appeared to show a war crime.

Two days ahead of key talks among the opposition in Qatar, the Syrian National Council lashed out at US accusations that it was not fully representative of the country’s diverse dissident forces.

“Any discussions aimed at passing over the Syrian National Council or at creating new bodies to replace it are an attempt to undermine the Syrian revolution by sowing the seeds of division,” the SNC said in a statement.

US Secretary of State Hillary Clinton this week voiced frustration with the SNC, saying it was not representative of on-the-ground opposition forces and that it “can no longer be viewed as the visible leader of the opposition”.

Reports have emerged that Washington will be pushing for an overhaul of the opposition at Qatar meeting, with longtime Syrian dissident Riad Seif touted as the potential head of a new government-in-exile dubbed the Syrian National Initiative.

Washington has accused the SNC of failing to unite the resistance to President Bashar al-Assad’s regime beyond a small group of Syrian exiles, of not representing the country’s diverse ethnic make-up and of alienating activists and rebel forces inside the country.

Rebel forces were making progress on the ground, however, with their fighters reported to have taken full control of a strategic crossroads Friday in a move that will further limit the regime’s ability to reinforce its troops in the northern commercial hub Aleppo.

Rebel attacks forced troops to pull back from their last position in the Saraqeb area where the roads to Aleppo from Damascus and from the Mediterranean coast meet, the Syrian Observatory for Human Rights said.

After seizing three checkpoints Thursday in attacks that killed 28 soldiers, the rebels now control an area extending 25 kilometres (15 miles) in all directions from the town, the Britain-based watchdog said.

The gains will help consolidate the rebels’ position in the northwestern Idlib province, where opposition forces early last month seized the town of Maaret al-Numan in a first blow to the government’s ability to resupply troops in Aleppo, where fighting has raged since mid-July.

At least 203 people, including 83 soldiers, were killed in fighting across Syria on Thursday, said the Observatory, which relies on a countrywide network of activists and medics in civilian and military hospitals.

It says more than 36,000 people have been killed since the uprising against Al Assad’s rule broke out in March 2011 as a protest movement inspired by the Arab Spring before escalating into an armed rebellion.

The rebels also faced criticism on Friday after a video appeared to show opposition fighters beating and executing soldiers after Thursday’s attacks on the Saraqeb checkpoints.

The video posted on YouTube — the authenticity of which could not be verified — showed about 10 soldiers being beaten, then lined up on the ground and executed with automatic rifles.

“It is very likely that this was a war crime, another one,” Rupert Colville, spokesman for UN High Commissioner for Human Rights Navi Pillay, told reporters in Geneva.

“We call on all parties to the conflict in Syria to respect international law,” he said.

Human rights group Amnesty International also raised concerns about the video, saying the footage “depicts a potential war crime in progress, and demonstrates an utter disregard for international humanitarian law by the armed group in question.”