Syrian army forces battled foreign-backed terrorists in Aleppo on Friday as President Bashar Assad pledged to use recapture of the city as a "springboard" for liberation of other areas.
Clashes were taking place on the northern and southern edges of the city, the so-called Syrian Observatory for Human Rights which is sympathetic to militants said.
It reported dozens of overnight airstrikes on eastern Aleppo which is under the control of Takfiri terrorists.
Russian aircraft, based the Hmeimim airfield in Syria, assist the Arab army in targeting terrorist positions in the city.
On Friday, President Vladimir Putin ratified an agreement with the Syrian government that allows Russia to use the air base indefinitely, the Kremlin said.
The ratification of the deal, which follows votes by both Russia's parliament and senate, comes as tensions with the West spike over Aleppo.
The US and its allies are angry over Syrian army advances in the city and have tried to bring them to a halt through pressuring both Damascus and Moscow.
US security meeting
Having cut off diplomatic talks with Russia after a ceasefire in Syria failed, President Barack Obama was to convene his National Security Council for a highly anticipated meeting on Friday.
US officials said Obama and his advisers were expected to consider their military and other options in Syria, Reuters news agency reported.
One set of options, the report said, includes direct US military action such as airstrikes on Syrian military bases, munitions depots or radar and anti-aircraft bases.
Reuters quoted an unnamed US official as saying that such a decision could raise the possibility of a direct confrontation with Russia that Obama has been at pains to avoid.
“US officials said they consider it unlikely that Obama will order US airstrikes on Syrian government targets, and they stressed that he may not make any decisions at the planned meeting of his National Security Council,” the news agency reported.
New arms for terrorists
One alternative, US officials said, is allowing allies to provide US-vetted militants with more sophisticated weapons, although not shoulder-fired anti-aircraft missiles.
The United States has been supporting so-called “moderate” militants fighting to topple President Assad.
However, a ceasefire agreement with Russia last month collapsed after the US failed to separate those militants from terrorists as the deal required.
On Thursday, Russia said it was prepared to secure safe passage for militants to quit Aleppo.
"We are ready to ensure the safe withdrawal of armed rebels, the unimpeded passage of civilians to and from eastern Aleppo, as well as the delivery of humanitarian aid there," Russian Lieutenant General Sergei Rudskoy said.
However, a new complication emerged after Britain's Foreign Minister Boris Johnson said his country was considering military options in the Syria conflict.
Johnson said the UK had "a very serious problem with Russia,” accusing Moscow of being “reckless and aggressive.”
Syrian government forces have encircled the eastern half of Aleppo, tightening the noose around terrorists holed up in the area.
In interview with Russian media outlet Komsomolskaya Pravda released on Friday, President Assad voiced his intention to recapture the northern city's militant-held neighborhoods.
“You have to keep cleaning this area and to push the terrorists to Turkey to go back to where they came from, or to kill them. There's no other option," he said.
Assad said the conflict in Syria is being used by the US as a way of retaining global dominance.
The US involvement in Syria "is about keeping the hegemony of the Americans around the world, not allowing anyone to be a partner on the political or international arena, whether Russia or even their allies in the West."
Assad said the source of the problem is terrorism and “no matter who's interfering in Syria now, the most important thing is who is supporting the terrorists on daily basis, every hour, every day."