GENEVA (AP) -- Syrian government forces on Tuesday called on opposition fighters in Aleppo to drop their weapons and surrender to authorities as they captured new ground on the northwestern edge of the city, tightening the siege on rebel-held parts of the metropolis where some 300,000 people live, activists said.
The push in which troops captured large parts of the city's Layramoun area came as state TV reported that the General Army Command informed residents of rebel-held parts of Aleppo via telephone text messages that the army has created several safe passages and makeshift centers for whoever wants to leave those areas.
The military warning comes days after the army fully encircled Aleppo, setting the stage for a prolonged siege aimed at eventually forcing the surrender of rebels holed up in the eastern parts of the city. Once Syria's thriving commercial center, Aleppo has been divided since 2012 between government- and rebel-controlled districts.
Dozens of people have been killed in the past few weeks amid intense fighting. Grim scenes of people trapped under the rubble of buildings have emerged and food shortages have been reported.
The U.N. humanitarian chief Stephen O'Brien told the Security Council Monday that Aleppo risks becoming the largest besieged area in the country. Food supplies are expected to run out in mid-August and many medical facilities continue to be attacked, he added.
In Geneva, the U.N. envoy for Syria said he aims to call a new round of talks between government and opposition envoys in Geneva "toward the end of August."
Staffan de Mistura said he wants to see the outcome of steps agreed upon in Moscow last week between the United States and Russia, in order "to make these talks particularly fruitful and hopeful" before setting a precise date.
The U.N. envoy spoke to reporters Tuesday after a closed-door meeting in Geneva with high-level U.S. and Russian diplomats. He said the discussion centered on initiatives about the "urgent need" for progress on issues like a widely violated ceasefire, humanitarian access, counter-terrorism and political transition in Syria.
Syrian government forces and their allies have been on the offensive around Aleppo, Syria's largest city, for weeks.
The army on Tuesday said it will keep providing Aleppo residents with basic necessities, but called all those living in rebel-held parts of the city to kick out "mercenaries and foreign fighters."
Baraa al-Halabi, an opposition activist in Aleppo, described the army claim about safe passages as "nonsense" and said he was not aware of any telephone messages sent to residents.
The Lebanese group Hezbollah's Al-Manar TV aired footage of government forces pushing in what appeared to be an industrial area near Aleppo. The station confirmed that President Bashar Assad's forces capture of areas in Layramoun and near Castello road, the main link between rebel-held parts of Aleppo and the rest of the country.
Earlier Tuesday, Russian Foreign Minister Sergey Lavrov said that recent U.S.-Russia discussions should encourage moderate Syrian opposition groups to leave areas occupied by al-Qaida's branch in Syria, thus helping to implement a truce. Lavrov spoke to Russian news agencies after talks in Laos with U.S. Secretary of State John Kerry, who visited Moscow earlier this month.
Moscow and Washington have differed over the role of the local al-Qaida branch known as the Nusra Front, with Russia calling the group terrorists and the U.S. asking Russia not to target them for fear of hitting the moderate opposition.
The U.S. has offered Russia a military partnership in Syria that includes intelligence and targeting sharing and even joint bombing operations.
The proposal would address the Nusra Front, which has presented one of the most persistent obstacles in enforcing a cease-fire in Syria. The group is engaged in a variety of local alliances with other rebel groups the U.S. and its Arab allies want shielded by the cessation of hostilities. The al-Qaida affiliate's fighters are often embedded with such groups on the battlefield or move between various militant formations.
The dispute over the Nusra Front has undermined the Russia- and U.S.-brokered truce with fighting continuing to rage in many areas in Syria. It has also fueled speculation of a potential split between Nusra and al-Qaida for practical purposes.
A Nusra Front official told The Associated Press on Tuesday that the group's leader Abu Mohammed al-Golani plans to announce a disassociation with al-Qaida soon. Speaking via text message from northern Syria, the official, who spoke on condition of anonymity because he was not authorized to speak publicly about the issue, said Nusra will merge with other insurgent groups.
Nusra Front is one of al-Qaida's most powerful branches around the world and reports about a possible disassociation with al-Qaida have circulated in the past but never materialized.
Some Nusra Front supporters said on social media that Nusra Front will change its name to The Front to Conquer the Levant. The activists even posted what they said is the group's new purported banner: White instead of black with the Muslim shahada on top and below it The Front to Conquer the Levant will replace the Nusra Front.
Mroue reported from Beirut. Natalya Vasilyeva in Moscow and Albert Aji in Damascus, Syria contributed to this report.