Syrian government forces at Aleppo's thermal power plant on Sunday after retaking the area as part of an offensive before a possible cease-fire takes effect. (George Ourfalian/AFP/Getty Images)

Russian President Vladimir Putin worked Wednesday to place himself in the center of efforts to secure a Syrian cease-fire, speaking by phone to the leaders of Syria, Saudi Arabia and Iran and drawing promises of cooperation, according to the Kremlin.

In a rapid-fire series of conversations, Putin bridged both sides of the conflict — Iran and Russia back Syrian President Bashar al-Assad and Saudi Arabia sides with rebel factions — and portrayed himself as bolstering the chances of a cessation of hostilities agreed to by Washington and Moscow earlier this week.

Assad called the proposals in the deal “an important step toward political settlement,” the Kremlin said in a statement. He also “confirmed the Syrian government’s readiness to facilitate the cease-fire’s implementation.”

But significant doubts remained about the viability of the plan, scheduled to take effect at midnight Friday.

Leading Syrian opposition groups have not yet committed to the deal. And both Russia and the United States say they will continue independent efforts to fight the Islamic State and an al-Qaeda-linked faction, Jabhat al-Nusra.

For months, Moscow has said it was battling the Islamic State, but Russian airstrikes also have targeted rebel groups, including some backed by the United States. Both Russia and Assad have labeled a broad swath of opponents of the Syrian government as terrorists.

Putin has seized on the cease-fire deal as a diplomatic victory for Russia and one that places Russia on the same superpower bargaining level as the United States, long a Kremlin goal. Wednesday’s phone calls appeared to be a continuation of that effort.

The joint discussions between the United States and Russia on Syria are leading “to a higher level of mutual confidence,” Putin spokesman Dmitry Peskov said Wednesday, the Interfax new agency reported. “At the same time, I'll repeat, once again, that the main goal in this case is to stop bloodshed in Syria, and so lay the groundwork for approaching a political settlement.”

The state-run Syrian Arab News Agency (SANA) reported that the Kremlin initiated the call with Assad.

Putin also spoke to Saudi Arabia’s King Salman, giving “a detailed explanation of the proposals” of the U.S.-Russian plan. On Wednesday, at least according to the Kremlin, Russia and Saudi Arabia put aside their differences over Syria and were in accord on the cease-fire plan.

“The king of Saudi Arabia welcomed the agreement and expressed his readiness to work together with Russia to implement” the plan, the Kremlin said.

Putin also spoke to Iranian President Hassan Rouhani, the Kremlin said.

Despite the Kremlin’s assurances that U.S. and Russian relations are improving as a result of the discussions, there have been mixed feelings in Washington about the accord.

Syrian forces backed by Russian airstrikes have pressed forward in a major offensive in the key northern city of Aleppo and elsewhere in the country, according to groups that monitor the fighting.

Russia and Syrian government forces, meanwhile, carried out heavy attacks against Islamic State positions near Aleppo on Wednesday amid a wave of bombings by the militant group, according to the Britain-based Syrian Observatory for Human Rights.

The monitoring group reported heavy fighting in a strategic village southeast of Aleppo that Islamic State militants seized Tuesday from forces loyal to Assad. The capture of Khanaser and the road leading to it has cut the government’s sole route linking the areas of Aleppo and other parts of the country under Assad’s control, according to the Observatory.

The fall of that road, if confirmed, would be a setback to Assad's Russian-backed offensive in Aleppo that has made startling gains against rebel groups.

A Russian Defense Ministry spokesman told journalists Wednesday that Russian jets in Syria had carried out 62 battle sorties in the past two days, including against targets near Aleppo, as well as in the provinces of Homs, Hama and the Islamic State stronghold of Raqqa.

The spokesman, Igor Konashenkov, claimed that the intensity of Russian airstrikes has fallen “especially in areas where local authorities and armed groups have agreed to cease hostilities and start negotiations.” While that data could not be independently verified, the ministry for several weeks earlier this month tallied an average of more than 60 strikes in Syria a day.

Those who are skeptical of Moscow’s efforts are pushing for war, Russian Foreign Minister Sergei Lavrov said Wednesday.

“Literally on the day when Russia and the United States approved the initiative on the cease-fire in Syria, voices could be heard from the capitals of the U.S. allies and from Washington which questioned the viability of this agreement," Lavrov said, according to the TASS news agency. "We want to say frankly that these voices are a call for war rather than for peace."

But even as support is drummed up for the cease-fire plan, it faced possible complications from neighboring Turkey, a NATO member which strongly backs anti-Assad forces.

In Ankara, Turkish President Recep Tayyip Erdogan urged that a Syrian Kurdish faction be excluded from the accord — a move that would allow Turkey’s military to continue cross-border shelling against the group.

Turkey has been urging the United States to sever ties with the Syrian Kurdish fighters, whose military wing is known at the People’s Protection Units, or YPG, on the grounds it has ties to a Turkish Kurdish faction that has waged a three-decade fight for greater autonomy. The Turkish Kurdish group, known as the Kurdistan Workers Party, is designated a terrorist organization by the United States and Turkey.

Erdogan questioned U.S. assertions that the YPG’s role in fighting the Islamic State makes it an indispensable ally, pointing out that the al-Qaeda-linked group Jabhat al-Nusra also battles the Islamic State.

Naylor reported from Beirut. Liz Sly in Istanbul contributed to this report.

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