BEIRUT (AP) — Syrian troops repelled a rebel advance near Aleppo on Monday, forcing opposition forces to retreat from positions they seized a day earlier as heavy fighting continued in the country’s largest city.

Russian Defense Minister Sergei Shoigu meanwhile said Moscow and Washington, which back opposite sides in the civil war, are edging closer to an agreement to defuse the fighting in the contested city.

“Step by step, we are nearing an arrangement, I’m talking exclusively about Aleppo, that would allow us to find common ground and start fighting together for bringing peace to that territory,” he said in remarks carried by Rossiya 24 television.

Russia has been launching airstrikes in support of President Bashar Assad’s forces for nearly a year, and Syrian and Russian warplanes have stepped up their raids in recent days in Aleppo and the rebel-held Idlib province nearby.

The Islamic State group, meanwhile, claimed responsibility for a suicide bombing that struck a bus transporting rebels through a border crossing between Syria’s opposition-held Idlib province and Turkey late Sunday, killing more than 30 fighters.

The Atmeh border post is one of several crossings Syrian rebels use to bring in fighters and supplies. The Syrian Observatory for Human Rights said the death toll from the bombing rose to 32.