BEIRUT (AP) -- A diplomatic push for a temporary pause in Syria's civil war and the delivery of humanitarian aid faced huge hurdles Friday, with Russia saying it would continue its airstrikes and government planes dropping leaflets urging rebels to surrender because "the belt is narrowing around you."
A plan for the "cessation in violence" announced by the U.S. and Russia does not go into effect for a week, and while the Syrian opposition expressed "cautious optimism," it also said more innocent civilians would be killed in that span.
Government forces, aided by a withering Russian bombing campaign, are trying to encircle rebels in Syria's largest city of Aleppo and cut off their supply route to Turkey. Another week of fighting could bring the Syrian troops closer to that goal.
Syrian forces recaptured several strategic hills north of Aleppo and are in position to target the final supply line to the rebel-held eastern suburbs, according to Al-Manar TV, a Lebanese channel run by the militant group and Syrian ally Hezbollah.
Heavy fighting between government and opposition forces occurred south of Aleppo, around the town of Tamoura, according to the Britain-based Syrian Observatory for Human Rights. It said 12 fighters of the al-Qaida-linked Nusra Front were killed.
U.S. Secretary of State John Kerry praised the agreement in Munich as a significant accomplishment in the five-year war, but he noted that a cessation of hostilities, if achieved, would only be a "pause" in the fighting and that more work would be needed to turn it into a full-fledged cease-fire.
He also said the agreements made were "commitments on paper" only. "The real test is whether or not all the parties honor those commitments and implement them," he told reporters after the nearly six-hour meeting concluded early Friday.
Kerry and Russian Foreign Minister Sergey Lavrov said a task force must try to deal with the "modalities" of the temporary truce. The task force will include members of the military along with representatives from countries that are supporting various armed groups in Syria. The Syrian government and the opposition would both have to agree to the details.
That could pave the way for a new round of peace talks between President Bashar Assad's government and the opposition, scheduled for Feb. 25 in Geneva. An earlier session broke down last week, due largely to gains by Assad's military helped by the Russian airstrikes.
The deal appeared to be the result of a compromise between the United States, which had wanted an immediate cease-fire, and Russia, which had proposed one to start on March 1.
Lavrov made clear that Moscow will continue airstrikes on Aleppo and other parts of Syria because they are targeting groups that are not eligible for the "temporary cessation of hostilities."
In the Syrian capital of Damascus, a member of Assad's ruling Baath Party told The Associated Press that the army's operations will continue against the Islamic State groups, the Nusra Front, and other factions that are close to them.
Parliament member Sharif Shehadeh said "the army aims to regain all Syrian territories and any part of Syria is a target for the army."
Syrian aircraft dropped leaflets over parts of Aleppo province telling militants to "drop your arms or this will be your fate." They bore a photo of the nearly naked, bullet-riddled body of a fighter and a Kalashnikov assault rifle by his side.
"The belt is narrowing around you more and more. Go back to where you came from. Surrender or you will face you inevitable fate," the leaflet read.
Kerry and Lavrov also announced an agreement to "accelerate and expand" deliveries of humanitarian aid to besieged Syrian communities beginning this week.
A task force began its first meeting in Geneva, with its leader, Jan Egeland, saying he hopes it can pave the way for aid to be delivered to besieged areas in Syria "without delay." He told reporters that he hoped aid could roll in "once we have all the access that we need."
A statement issued later said sustained delivery of assistance is expected to "begin this week to besieged areas where civilians are in desperate need of assistance. Humanitarian access to these most urgent areas will be a first step toward full, sustained, and unimpeded access throughout the country."
"Once we get clearance by concerned parties, the U.N. and its humanitarian partners will be able to reach the civilians in need within the coming days," the statement quoted U.N. Special Envoy to Syria Staffan de Mistura as saying.
Since Feb. 1, Syrian troops and their allies, including Iranian-backed groups, have captured wide areas in the north near Aleppo, the provincial capital and once commercial center. They also advanced in the southern province of Daraa that borders Jordan.
A cessation of hostilities "likely represents an opportunity for Russia, Iran and the Syrian government to help secure recent Syrian government and allied militias' gains, while providing relief to key towns and neighborhoods," said Firas Abi Ali, an analyst with the think tank IHS Jane's.
Despite apparent concessions on potential timing of the truce and the agreement to set up the task force, the U.S., Russia and others remain far apart on which groups should be eligible for it. The new task force will take up a job that was supposed to have been settled months ago. At the moment, only two groups - the Islamic State and the Nusra Front - are ineligible because they are identified as terrorist organizations by the U.N.
"If the cease-fire does not include Daesh and Nusra this means that it will not include most of the territories that are witnessing battles," said Ibrahim Hamidi, a journalist who covers Syrian affairs for the Saudi-owned newspaper Al Hayat. He used an Arabic acronym to refer to IS.
Russia, Syria and Iran argue that other groups, notably some supported by Turkey, Saudi Arabia and other Arab states, should not be eligible for the cease-fire, and there was no sign Friday that those differences had been resolved.
Five years of conflict have killed more than a quarter-million people, created Europe's biggest refugee crisis since World War II and allowed the Islamic State to carve out its own territory across parts of Syria and neighboring Iraq.
Lee reported from Munich. Associated Press writers Nataliya Vasilyeva in Moscow, Jamey Keaten in Geneva, Zeina Karam in Beirut, Bradley Klapper in Washington, Albert Aji in Damascus, Syria, and Geir Moulson in Munich contributed to this report.