On Saturday, Syrian rebels cut a newly built bypass road linking the capital Damascus with the northern city of Aleppo, an activist group said, while state media reported that government troops have secured a strategic highway between the capital and the southern city of Daraa.
The reported fighting came as an activist group said U.S. ambassador to Syria Robert Ford, who left the country last year, met with a rebel commander at a border crossing point with Turkey.
The Aleppo Media Center said Ford met on Thursday with Col. Abdul-Jabbar al-Akidi, head of Aleppo province's rebel military council at the Bab al-Salama border crossing point.
It posted a picture and a video of the two men standing on a road just a few yards outside a fence that appeared to be the border between Turkey and Syria.
The AMC quoted al-Akidi as calling on the U.S. to lift an arms embargo imposed on rebels.
The U.S. so far has balked at sending weapons to the rebels, fearing the arms could end up in the hands of al-Qaida-linked groups or other extremists in the opposition ranks.
Ford was in Turkey to get the opposition to commit to a proposal presented last year at an international conference in Geneva that involves talks with the regime of President Bashar Assad.
The visit follows a decision by Russia and the U.S. this week to convene an international conference to bring representatives of the Assad regime and the opposition to the negotiating table. No date has been set.
The plan, similar to the one set out last year in Geneva, calls for talks on a transitional government and an open-ended cease-fire.
Such efforts have run aground in the past, but U.S. Secretary of State John Kerry said there was a chance it might work this time.
"If the political willpower is there and shared, and if people are prepared to compromise reasonably, there is a path forward to be able to have a peaceful solution in Syria," he said late Friday.
The regime and the Syrian opposition have welcomed the idea, but with conditions. The opposition says talks can only begin once Assad and his aides have left.
The regime says it will keep fighting the rebels, without saying at which stage it would be willing to halt its fire.
In Israel, meanwhile, an official confirmed that Prime Minister Benjamin Netanyahu will soon meet Russian President Vladimir Putin, an Assad ally.
Israel has expressed concern over what Israeli officials say is an imminent sale of advanced Russian anti-aircraft missiles to Syria.
Israel is worried that advanced Russian weapons could reach militant groups hostile to the Jewish state, such as Hezbollah in Lebanon.
In northern Syria, rebels took over two army posts on a desert road that serves as an alternate route into the city of Aleppo after days of fighting, said Rami-Abdul-Rahman, who heads the Britain-based Syrian Observatory for Human Rights.
The regime built the desert road to bypass contested areas after rebels captured the town of Maaret al-Numan in October, cutting the main highway between Aleppo and Damascus.