ALEPPO, Syria, Sept. 14 (UPI) -- As humanitarian aid to Syria waits at the Turkish border, the United States and Russia agreed Wednesday to extend the truce by another 48 hours.
"They agreed to discuss and agreed to extend the cessation for another 48 hours," spokesman Mark Toner said, "with the goal being that this would last seven days and then we would move to the next step."
The extension was agreed to after various reports of cease-fire violations by both the Syrian government and opposition factions.
"We've seen violations by both sides. And look, we've always been clear, just as we have said that Russia's responsibility is to exert influence or put pressure -- however you want to put it --- on the regime to abide by the cessation of hostilities, it is incumbent on us to persuade the moderate opposition to also abide by the cessation of hostilities," Toner added.
Russian General Staff official Viktor Poznikhir said earlier that the terms of the original pact have generally been adhered to by both sides, although he claimed rebel forces had committed about 60 violations since the cease-fire started Monday.
A Syrian military source said armed rebel groups broke the truce Wednesday morning with seven mortar shells in the western and northern countryside. The Syrian Observatory for Human Rights, a pro-opposition monitoring group, said pro-regime forces shelled Aleppo and two towns in the northern countryside.
The Russian military also announced it carried out airstrikes on Islamic State militants in Syria who were preparing an assault on the ancient city of Palmyra, which was liberated from the terrorists earlier this year. According to the Russian General Staff, the strikes killed 250 IS militants.
Al Jazeera reported that Syrian President Bashar al-Assad's regime was not allowing any humanitarian aid from Turkey to enter the rebel-held Aleppo -- likely because Turkey has supported anti-government rebels.
"Since the very beginning of the crisis in Syria, Turkey has always provided support to the armed terrorist organizations and supplied them with money, arms, not to mention harboring terrorists, assisting them and bringing mercenaries from all over the world to murder the Syrian people and destroy their country," Syria's foreign ministry said.
A Turkish Red Crescent official told Al Jazeera on Wednesday its aid trucks were still at the Cilvegozu border crossing in Hatay. The trucks will be using only U.N. flags, as requested by Russia, the official said.
Staffan de Mistura, United Nations special envoy for Syria, told reporters in Geneva on Tuesday he hoped the convoys could start deliveries later Wednesday to the estimated 250,000 civilians in rebel-held areas in eastern Aleppo.
Jens Laerke, a spokesman for the U.N.'s humanitarian office, said, "We need to enter an environment where we are not in mortal danger."
The truce, reached last week by U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov, began at sunset on Monday, coinciding with the major Muslim holiday of Eid al-Adha. The two-day truce was the first step of a proposed seven-day truce.