The Syrian army announced late Monday that it had extended the truce in Aleppo and its countryside for 48 hours, according to state media.
The ceasefire would be extended from 0100 local time Tuesday until 2400 on Wednesday, the state-run Syrian News Agency (SANA) reported.
Earlier Monday Russia and the United States vowed to put pressure on both the Syrian government and rebel forces to shore up a crumbling ceasefire after more than two weeks of deadly clashes and airstrikes in the north of the country.
A joint statement from the two countries said that Moscow, a close ally of Syrian President Bashar al-Assad, would "work with Syrian authorities" to cut down on air operations over civilian areas.
Airstrikes on a hospital and a refugee camp in rebel-held areas of northern Syria in recent weeks killed an estimated 80 people, causing international outrage. The opposition, which has no air force, blamed the government for both strikes.
Moscow and Washington said they had "re-emphasized the terms" of the cessation to field commanders on all sides, especially in the northern city of Aleppo, the outskirts of Damascus and the northern Latakia region where heavy fighting has taken place since mid-April.
They also pledged to press the two sides to ensure aid delivery to besieged areas, including Daraya and other rebel-held towns near Damascus.
Opposition negotiators cited government obstruction of aid deliveries to Daraya and other areas as one of the reasons for suspending their participation in peace talks in Geneva last month.
The statement came as key countries backing the Syrian opposition met in Paris at the invitation of French Foreign Minister Jean-Marc Ayrault as a recourse to the stalled peace talks.
Officials from Germany, the US, Saudi Arabia, the United Arab Emirates, Italy, Qatar, Turkey, the European Union, Britain and Jordan were to take part in the meeting, along with Riad Hijab, coordinator of the Syrian opposition High Negotiations Committee.
Speaking to reporters in Paris, German Foreign Minister Frank-Walter Steinmeier said the group would observe the way Monday's statement from Russia and the US impacts conditions on the ground in Aleppo.
He added that they would reconvene on Tuesday in Vienna to assess the impact.
France's Ayrault accused the regime of not putting forth any concrete proposals in Geneva and of undermining the principles of the revived peace process launched in Vienna last year.
He described Monday's meeting as a mobilization of the international community but said it was not meant to replace the meetings of the International Syria Support Group, which brings together outside backers of both the Syrian government and the opposition, including the US, Russia, Iran and Saudi Arabia.
The French foreign minister and US Secretary of State John Kerry were due to meet for a working dinner after the Syria conference. Kerry was also to meet with German Foreign Minister Frank-Walter Steinmeier on Tuesday morning before travelling to Britain.
Aleppo, where 50 people died in the airstrike on the al-Quds hospital, has been the focus of recent international talks.
The implementation of the cessation of hostilities there is complicated by the active role on the rebel side of Syrian al-Qaeda affiliate the al-Nusra Front. As a UN-designated terrorist group, it is excluded from the terms of the cessation.
Rebel forces spearheaded by al-Nusra made advances south of the city last week, and rebels inside the city have shelled the government-held western sector despite a Russian-announced truce that began on Thursday.
Retaliatory shelling and government airstrikes have claimed a total of almost 300 civilian lives in the city since April 22, according to the Syrian Observatory for Human Rights, a monitoring group.
Late Monday, at least ten people - including three children - were killed and 12 others injured when regime planes struck the north-western Syrian village of Hafrserja, on the outskirts of Idlib, the Britain-based Syrian Observatory said.
