Fierce fighting raged Friday in Syria's east, where rebels killed a top intelligence officer and executed 10 soldiers, as the United States pushed for new peace talks.
US officials said Secretary of State John Kerry would head to Europe for discussions on a planned peace conference in Geneva, which a Syrian official said could come at the end of November.
But the prospects for the conference, dubbed Geneva 2, remain unclear, with the Syrian opposition divided and due to vote next week on whether to take part.
On the ground, the Syrian Observatory for Human Rights reported fierce clashes that began in the eastern province of Deir Ezzor overnight continued on Friday.
The group, which relies on a network of activists, doctors and lawyers, also reported regime air strikes wounded several people and damaged homes in Deir Ezzor city.
They followed rebel advances in the Rashdiya neighbourhood, where a top intelligence officer Major General Jamaa Jamaa was killed on Thursday.
State television said Jamaa was "martyred while carrying out his national duties to defend Syria and its people and pursuing terrorists in Deir Ezzor".
The Observatory said Jamaa, who was in charge of military intelligence in Deir Ezzor province, was hit by sniper fire during clashes in Rashdiya between troops and jihadist fighters.
It also reported that fighters of the Al-Qaeda-linked Al-Nusra Front executed 10 soldiers after capturing them during the clashes.
The fighting came a day after Syria's Deputy Prime Minister Qadri Jamil said proposed peace talks in Geneva could take place on November 23-24.
"We are closer than ever to holding the Geneva 2," he said in Moscow, though Russia's foreign ministry quickly pointed out that the UN would decide the timetable.
Speaking on US radio, Kerry insisted on the need to "move forward" the peace process on Syria.
"There is no military solution, absolutely not," he said.
"So we are trying to move the process forward. I'll have meetings next Tuesday in London with the support group of the opposition."
On Tuesday, Kerry and other officials are due to attend, alongside the Syrian opposition, a meeting of the so-called Friends of Syria in London to review progress towards convening the Geneva conference.
Whenever the conference is held, the prospects for a negotiated solution to the conflict remain slim, with Syria's opposition divided on even attending peace talks.
The National Coalition, Syria's main opposition bloc, said it would hold internal discussions next week to decide whether to attend the conference.
The Syrian National Council, a key member of the Coalition, has already said it opposes the Geneva conference and threatened to quit if the umbrella group takes part.
The international community has for months been pushing Syria's rebels and the regime to participate in talks on a negotiated solution to the conflict, which has killed an estimated 115,000 people since March 2011.
But the government of President Bashar al-Assad says his departure from office will not be on the table, while the opposition insists he cannot remain in power.
The renewed push for the peace talks, which were mooted as early as May this year, comes after a September deal under which Syria agreed to turn over its chemical arsenal for destruction.
The agreement, enshrined in a UN Security Council resolution, staved off threatened US military action against Assad's regime after an August 21 sarin attack outside Damascus that killed hundreds.
A team from the United Nations and the Organisation for the Prohibition of Chemical Weapons has been in Syria since October 1 to oversee the destruction of its chemical arms by mid-2014.
On Thursday the OPCW, which was awarded the Nobel Peace prize for its work, said nearly half of its inspections were complete, but said security remains a key concern.
"We have done nearly 50 percent of the verification work of the facilities that have been declared to us," said Malik Ellahi, a political adviser on Syria for the OPCW.
The mission has key deadlines it must meet, including verifying Syria's disclosed chemical weapons, identifying key equipment, destroying production facilities and starting the destruction of Category 3 chemical weapons by November 1.