A pullout by the Local Coordination Committees from the Syrian National Council (SNC) would be a blow for the group, which is already facing political and organizational challenges in its quest to oust President Bashar al-Assad.
And if the SNC continues to deteriorate, it could complicate efforts for the West and others to get behind the opposition.
Fifteen months into the uprising, Syria's opposition is still struggling to overcome infighting and inexperience, preventing the movement from gaining the traction it needs to present a credible alternative to Assad. Its international backers have repeatedly appealed for the movement to pull together and work as one unit.
The SNC, whose members are largely Syrian exiles, has tried with little success to gather the opposition under its umbrella and has alienated minorities inside Syria, including the Kurds and Alawites. Other opposition groups accuse it of trying to monopolize power.
Several prominent dissidents, including Haitham al-Maleh and Kamal al-Labwani, have already quit the SNC, calling it an “autocratic” organization.
In Thursday's statement, the LCC -- a network of activists based both inside and outside of Syria -- accused the SNC leadership of marginalizing council members and acting alone on major decisions. It threatened to suspend its membership in the council and later withdraw altogether if its concerns are not addressed.
“We have seen nothing except political incompetence in the SNC and a total lack of consensus between its vision and that of the revolutionaries,” the statement said.
The LCC said the council has “drifted away from the spirit of the Syrian revolution in its quest for a civil and democratic state based on the principles of transparency and transfer of power.”
Earlier this week, Burhan Ghalioun was re-elected to a third, 3-month term as head of the SNC. A Sunni Muslim professor at the Sorbonne in Paris who has led the council since its formation in September, he has been criticized by some opposition figures of being too close to the Muslim Brotherhood and of being out of touch with the reality on the ground in Syria.
Ghalioun ran against George Sabra, a Christian council member seen by many as a better choice to soothe concerns by Syria's religious minorities, some of whom have remained loyal to Assad out of fear for their future in case his regime collapses.
In a televised interview following his re-election, Ghalioun acknowledged divisions within the SNC and said the group was working on a new strategy.
Unlike Libya's National Transitional Council, which brought together most factions against Muammar Gaddafi's regime and was quickly recognized by much of the international community, Syria's opposition has no leadership on the ground and has not been officially recognized by significant powers.
Assad says terrorists are behind unrest
In his first interview since December, Assad insisted his regime is fighting back against foreign mercenaries who want to overthrow him, not innocent Syrians aspiring for democracy in a yearlong uprising.
The interview with Russian TV showed Assad is still standing his ground, despite widespread international condemnation over his deadly crackdown on dissent.
“There are foreign mercenaries, some of them still alive,” Assad said in an interview broadcast Wednesday on Russian state news channel Rossiya-24. “They are being detained and we are preparing to show them to the world.”
Assad also cautioned against meddling in Syria, warning neighboring nations that have served as transit points for contraband weapons being smuggled into the country that “if you sow chaos in Syria you may be infected by it yourself.”
He did not elaborate, but the opposition and anti-regime activists say Syrian forces have mined many of the smuggling routes where weapons flow into Syria -- mainly from neighboring Turkey and Lebanon.
Assad, who inherited power from his father in 2000, still has a firm grip on power in Syria some 14 months into a revolt that has torn at the country's fabric and threatened to undermine stability in the Middle East.
The UN estimated in March that the violence has killed more than 9,000 people, and hundreds more have been killed since then as a revolt that began with mostly peaceful calls for reform transforms into an armed insurgency.
A group known as the Free Syrian Army is determined to bring down the regime by force of arms, targeting military checkpoints and other government sites.
A UN observer team with more than 200 members has done little to quell the bloodshed, and some even have been caught up in the violence themselves.
Six observers had to be evacuated from a northern town controlled by the opposition Wednesday, a day after a roadside bomb hit their convoy and left them stranded overnight with opposition forces. None of the observers was wounded, and it was not clear who was behind the attack.
The shooting started as the convoy arrived in the opposition area, said Ahmad Fawzi, spokesman for international envoy Kofi Annan.
“The UN observers were in their cars and heard the shooting but did not witness anyone being killed, nor could they ascertain the direction of the fire,” he said. “At the same time, the bomb exploded near one of the vehicles, damaging the hood.”