MOSCOW -- Russia's defense ministry said Tuesday that its military at the Russian air base in Syria was preparing for some of the planes and fighter jets to leave and return home.

Tuesday's statement came a day after President Vladimir Putin ordered the Russian military to withdraw most of its forces from Syria, timing his move to coincide with the resumption of the Syrian peace talks in Geneva.

It is an end game that allows the Russian leader, as the war in Syria enters its sixth year, to cash in on his gains and reduce his risks in the gruelling conflict.

The ministry said Russian personnel were loading equipment and materiel onto cargo planes and getting ready for the withdrawal, which marks an end to Russia's five-and-a-half-month air campaign. The ministry later said the first group of Russian warplanes had departed Syria.

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Russian airstrikes have allowed Syrian President Bashar Assad's army to win back some key ground and strengthen his positions ahead of the Geneva talks.

The ministry did not indicate when the first planes were scheduled to leave.

With Russia's main goals in Syria achieved, the pullback will allow Putin to pose as a peacemaker and help ease tensions with NATO member Turkey and the Gulf monarchies vexed by Moscow's military action.

At the same time, Putin made it clear that Russia will maintain its airbase and a naval facility in Syria and keep some troops there. Syria's state news agency also quoted Assad as saying that the Russian military will draw down its air force contingent but won't leave the country altogether.

The Syrian presidency said Assad and Putin spoke on the phone Monday and jointly agreed that Russia would scale back its forces in Syria. It rejected speculation that the decision reflected a rift between the allies and said the decision reflected the "successes" the two armies have achieved in fighting terrorism in Syria and restoring peace to key areas of the country.

The Syrian army said it would continue its operations against the Islamic State of Iraq and Syria (ISIS), and al Qaeda's branch in Syria, the Nusra Front, and other terrorist organizations "with the same tempo."

Announcing his decision in a televised meeting with Russia's foreign and defense ministries, Putin said the Russian air campaign has allowed Assad's military to "radically" turn the tide of war and helped create conditions for peace talks.

Russian President Vladimir Putin meets Foreign Minister Sergei Lavrov at the Kremlin in Moscow, Russia, March 14, 2016. REUTERS

"With the tasks set before the Defense Ministry and the military largely fulfilled, I'm ordering the Defense Minister to start the pullout of the main part of our group of forces from Syria, beginning tomorrow," Putin said.

He also informed President Obama of his move in a phone call, emphasizing the importance of U.S.-Russian coordination "for preserving the cease-fire, ensuring humanitarian aid deliveries to the blockaded settlements and conducting an efficient struggle against terrorist groups," according to the Kremlin, which added that the conversation was "business-like and frank."

Putin didn't specify how many planes and troops would be withdrawn. The number of Russian soldiers in Syria has not been revealed. U.S. estimates of the number of Russian military personnel in Syria vary from 3,000 to 6,000.

Russia has deployed more than 50 jets and helicopters to its Hemeimeem air base, in Syria's coastal province of Latakia, and they have operated at a frenetic pace, each flying several combat sorties on an average day. Russian Defense Minister Sergei Shoigu reported to Putin that thanks to the Russian air support the Syrian military has extended its control to 400 towns and villages over an area of about 6,000 square miles.

State TV quoted Assad as saying that the collaboration between Russian and Syrian forces has secured "victories against terrorism and returned security to the country."

A White House statement said Mr. Obama welcomed Russia's move, but also noted continued sporadic violence and urged Putin to pressure the Syrian regime to stop offensive actions that could undermine the fragile truce.

The U.N. special envoy for Syria, Staffan de Mistura, who restarted peace talks between the Syrian government and the opposition in Geneva on Monday, said he had no comment on Putin's announcement when contacted by The Associated Press.

Earlier in the day, he warned that the only alternative to the negotiations is a return to war, and described political transition in the country as "the mother of all issues."

The Russian- and U.S.-brokered cease-fire that began on Feb. 27 has largely held, but both the Syrian government and its foes have accused one another of violations. The deal with Washington has achieved a key Putin goal: raising Russia's global profile to appear as an equal to the United States in mediating the Syrian conflict that has dominated global attention.

ISIS and the Nusra Front are excluded from the cease-fire and Russia has said it would continue its fight against the groups considered terrorists by the United Nations.

A Pentagon spokesman, Navy Capt. Jeff Davis, said the Russians in recent days have been pounding ISIS targets in and around the western approaches to the city of Palmyra, which is firmly in ISIS control. Davis said this has been a Russian focus since the cessation of hostilities began.

Although Putin's announcement caught Pentagon officials by surprise, officials have said they had questioned how long the Russian air campaign would last based on the fact that they were not making regular troop rotations.

Syrian opposition spokesman Salem Al Mislet, in Geneva, cautiously welcomed Putin's move, but urged the Russian leader to withdraw his support for Assad.

"If this step, this action will remove all Russian troops from Syria then it will be a positive step, I believe," he said, adding that Putin should follow up on that "by saying he is standing beside the Syrian people, not beside the Syrian dictatorship."

Moments before meeting with a Syrian government envoy in Geneva, de Mistura laid out both high stakes and low expectations for what is shaping up as the most promising initiative in years to end the conflict that moves into its sixth year on Tuesday. At least a quarter of a million people have been killed and half of Syria's population has been displaced, flooding Europe with refugees.

The truce, however, has helped vastly reduce the bloodshed and allowed the recent resumption of humanitarian aid deliveries to thousands of Syrians in "besieged areas" -- zones surrounded by fighters and generally cut off from the outside world.

De Mistura laid out a stark choice for Syrian parties in the talks, saying: "As far as I know, the only plan B available is return to war -- and to even worse war than we had so far."

The two sides are deeply split on Assad's future. His foreign minister, Walid al-Moallem, said Saturday that any talk of removing Assad during a transitional period sought by the U.N. is "a red line," and rejected the international call for a presidential election to be held within 18 months -- a key demand of the opposition.

But de Mistura, keeping to language laid out in the U.N. Security Council resolution in December that paved the way for the talks, insisted that political change, including a timetable for new elections within 18 months, is the ultimate goal.

"What is the real issue - the mother of all issues? Political transition," he said.