BEIRUT (AP) -- Russian President Vladimir Putin spoke Wednesday with key players in the Syria conflict, including President Bashar Assad, ahead of a U.S.-Russia-engineered cease-fire, as the opposition voiced concerns that the truce due to begin later this week will only benefit the Syrian government.
Government troops backed by Russian warplanes waged fierce battles to regain control of a strategic road southeast of Aleppo from the Islamic State group. The extremist group seized the town of Khanaser and surrounding hills on Tuesday, cutting the main land route to Aleppo.
The state-run news agency said 18 people were killed in IS shelling of government-held neighborhoods in the city over the past 24 hours.
A key element of the agreement on a "cessation of hostilities" is humanitarian access to besieged and hard-to-reach areas.
The United Nations announced the first high-altitude airdrop of 21 metric tons of aid Wednesday over Deir el-Zour, which is under siege from Islamic State extremists. But the World Food Program said later it faced "technical difficulties" and indicated the drop may have been off target.
The truce agreement, which is set to take effect at midnight Friday local time, does not cover the Islamic State group, Syria's al-Qaida branch known as the Nusra Front, or any other militia designated as a terrorist group by the U.N. Security Council.
It's not clear exactly where along Syria's complicated front lines the fighting would stop and for how long — or where counterterrorism operations could continue. Also unresolved are how breaches in the truce would be dealt with.
It remains shaky at best and major questions over enforcement are still unresolved.
In a further reflection of the complicated terrain, Turkey's president said Wednesday that a U.S.-backed Syrian Kurdish militia group — which Turkey regards as a terror organization — should also be kept outside of the scope of the agreement. Turkey has in the past few weeks been shelling the group known as the People's Protection Units, or YPG, in northern Syria.
The comments by President Recep Tayyip Erdogan suggested Turkey may not stop bombarding the group, which has been a key fighting force against IS.
Addressing dozens of local administrators in Ankara, Erdogan also voiced serious concern that the proposed truce will strengthen Assad and lead to "new tragedies."
Although it has committed in principle to the truce, the main Syrian opposition umbrella group is deeply skeptical and has kept its meetings in Riyadh, Saudi Arabia, open while it seeks clarifications from the U.S. about the mechanism for the implementation of the agreement.
Salem Al Meslet, spokesman for the alliance known as the High Negotiations Committee which groups political and rebel factions, said his group has "major concerns" that Russia and Assad's forces will continue to strike at mainstream rebels under the pretext of hitting "terrorist groups" during the truce.
However, in a telephone interview with The Associated Press, he reiterated that the opposition wants to stop the bloodshed and would abide by the truce in principle.
"The Americans are taking note of our concerns and we are waiting for their replies," Al Meslet said.
The U.S. is hoping that a cessation of hostilities would reduce the violence in Syria enough to bring the two sides back to the negotiating table in Geneva to discuss a roadmap for a political transition that was unanimously adopted by the U.N. Security Council in December.
Staffan de Mistura, the U.N. special envoy for Syria who led the last round of talks, is expected to brief the Security Council on Friday.
He is likely to call for new talks between the government and opposition on March 4, a council diplomat said Wednesday, speaking on condition of anonymity because consultations have been private.
U.S. Secretary of State John Kerry told American lawmakers on Tuesday that he would not vouch for the success of the cease-fire agreement but that it is the best pathway for ending five years of violence in Syria that has killed more than 250,000 people and displaced another 11 million.
On Wednesday, Assad and Putin discussed the truce agreement in a phone call. SANA said the two leaders stressed the importance of continuing to fight the Islamic State group, Nusra Front "and other terrorist organizations."
Putin's spokesman, Dmitry Peskov, said there were differences in opinion between Moscow and Damascus but that Russia is one of the few countries still in contact with "the legitimate Syrian leader." He did not elaborate.
Speaking in a conference call with journalists, he said Moscow was doing its part and expects the United States to do the same to make sure the groups it supports adhere to the cease-fire.
"The main goal is to stop the bloodletting in Syria," he said.
Asked whether Moscow had a Plan B in case the truce did not hold, he replied: "We are concentrating on Plan A right now. ... It's too early to speak of other plans."
The Russian military later said its coordination center in Syria has helped negotiate the cessation of hostilities in some areas as part of efforts to implement the cease-fire deal.
Russian Defense Ministry spokesman, Maj.-Gen. Igor Konashenkov, said the center, located at Syria's Hemeimeem air base which is hosting Russian warplanes, has received several requests for assistance from various opposition groups.
He said cease-fire declarations already have been signed by the government and opposition representatives in several areas in the provinces of Homs and Latakia.