The Russian air force and Syrian military are preparing a joint operation to take Aleppo from rebels, the Syrian Prime Minister was quoted saying on Sunday, and an opposition official said a ceasefire was on the verge of collapse.
With a UN envoy due in Damascus in a bid to advance struggling diplomatic efforts, the ''cessation of hostilities agreement'' brokered by Russia and the United States came under new strain as government and rebel forces fought near Aleppo.
The ceasefire came into effect in February with the aim of paving the way for a resumption of talks to end the five-year-long war. But it has been widely violated, with each side blaming the other for breaches. The fighting south of Aleppo marks the most significant challenge yet to the truce deal signed.
Diplomacy has meanwhile made little progress with no compromise over the future of President Bashar Al-Assad, his position strengthened by Iranian and Russian military support.
Syrian Prime Minister Wael al-Halaki told a delegation of visiting Russian lawmakers of preparations to ''liberate'' Aleppo, Syria's biggest city and commercial hub before the conflict that erupted in 2011. The city of Aleppo is divided into areas controlled separately by the government and opposition.
''We, together with our Russian partners, are preparing for an operation to liberate Aleppo and to block all illegal armed groups which have not joined or have broken the ceasefire deal," he was quoted as saying by TASS news agency.
Dmitry Sablin, a member of Russia's upper house of Parliament and a member of the delegation, told RIA news agency ''Russian aviation will help the Syrian Army's ground offensive operation''.