The rebel Free Syrian Army has appointed a new commander, after months of losing ground to both government forces and Islamist fighters.
The Western-backed, moderate forces cited the ineffectiveness of Salim Idris, and said he has been replaced by Abdul-Ilah al-Bashir.
The office of Syrian National Coalition President Ahmad Jarba praised the move in a statement Monday, and reiterated the opposition group's determination to go up against government troops and al-Qaida-linked militants.
Meanwhile, U.S. Secretary of State John Kerry says the Syrian government is trying to win a military victory over the opposition, and that Russia is enabling President Bashar al-Assad on that path.
Kerry said Monday in Jakarta that Syria's strategy is evident in its continuing barrel bombing of civilians, and that Russia's deliveries of arms and aid are helping Mr. Assad's pursuit of a military solution over a political end to the civil war.
"It is very clear that Bashar al-Assad is continuing to try to win this in the battlefield rather than to come to the negotiating table in good faith."
Michael O'Hanlon, a senior fellow at the Brookings Institution agreed with Kerry's assessment during an interview with al-Hurra on Monday.
"Assad sees no need to compromise. And his sponsors -- Russia, Iran, Hezbollah -- are playing very seriously in this game. Whereas the supporters of the opposition are playing with one hand tied behind their back. "
VOA correspondent Scott Stearns, who is traveling with Kerry, said the secretary wants the international community to use a break in the talks to figure out how best to pursue a political solution.
"He said the United States still believes that there is no military solution to the war in Syria, but it's his opinion that Syrian President Bashar al-Assad is pursuing just that, a military solution, a military solution in the opinion of the United States that's aided by Iran, Hezbollah and Russia. He said Russia needs to stop being part of the problem and play a more active role in being a part of the political solution."
Russia has been both an ally of Mr. Assad and, along with the United States, a lead player in bringing the Syrian sides together for the peace talks. Russian Foreign Minister Sergei Lavrov said his government is working with Syrian officials daily, and that more of Syria's problems are being caused by terrorists and extremists.
On Sunday, Kerry said in a statement that all parties involved in the peace talks knew they would be difficult, but that "obstruction" by the Assad government is making the process even harder. He also praised Syrian opposition groups, saying they have presented a "viable and well-reasoned roadmap" for a transitional government in Syria.
Syrian Foreign Minister Walid al-Moallem cast blame at the United States, saying it worked to create a negative climate at the negotiations in Geneva.
O'Hanlon stopped short of blaming the U.S., but said the attitude had to change in the West.
"Until Washington and other capitals get more serious about helping the opposition, there is no realistic hope for peace."
The second round of peace talks ended Saturday with no agreement. A third round of negotiations has not been scheduled.
Also Sunday, the United Nations said it was not able distribute food aid for a ninth consecutive day at the Yarmouk refugee camp in Damascus, which is home to thousands of Palestinians who have been there since before the Syrian civil war began.
A U.N. spokesman called on authorities and all parties to allow food, medicine and other humanitarian aid to be distributed, saying it is "a matter of the greatest urgency."
Kerry is traveling Monday to Abu Dhabi, where the Syrian crisis will be part of his meetings with officials.
"As you know, the Gulf states have largely pushed for a more active military presence in support of the opponents of Syrian President Bashar al-Assad. There's been some disagreement among some Gulf allies of the United States who feel that Washington has not done enough militarily to actively support the Syrian opposition."
The secretary's talks in Abu Dhabi will also include the Israeli-Palestinian peace process and Iran's nuclear program.