Russian President Vladimir Putin Thursday accused the West of playing a "double game" with terrorist groups in Syria, where both Moscow and a U.S.-led coalition are conducting separate bombing campaigns. "It's always difficult to play a double game: declaring a fight against terrorists while simultaneously trying to use some of them to arrange the pieces on the Middle East chess board in one's own interests," Putin said at a meeting of political scientists in Sochi known as the Valdai Club. "It is impossible to prevail over terrorism if some of the terrorists are being used as a battering ram to overthrow undesirable regimes," Putin said. Russian Foreign Minister Sergey Lavrov is set to meet U.S. Secretary of State John Kerry, as well as their Turkish and Saudi counterparts, Feridun Sinirlioglu and Adel al-Jubeir, respectively, in Vienna Friday for crucial talks on the Syrian conflict, a 4-year-old war that has killed more 250,000 people and forced millions from their homes. The high-level meeting follows the surprise visit of Syrian President Bashar Assad to Moscow for talks with Putin Tuesday, the embattled leader's first foreign visit since 2011. Russia – which has pledged to support Damascus militarily, much to the West's dismay – has insisted the airstrikes it has conducted since Sept. 30 in the war-torn country are hitting ISIS and other "terrorist" groups, and are being conducted at the Syrian leadership's request. But the U.S. and its allies, who are conducting a separate bombing campaign in the country, say Moscow's strikes are aimed at Western-backed moderate rebels fighting Assad. "There is no need to play on words, to classify terrorists as moderate and nonmoderate," Putin said. "What is the difference?" he said, suggesting that "in the opinion of some experts ... so-called moderate bandits behead people moderately or gently." During his encounter with Assad, Putin called for a political solution involving all groups to try to end the war, the Kremlin said. Kremlin spokesman Dmitry Peskov later declined to comment on whether Assad's future in Syria had been discussed during the encounter. Assad, who last visited Russia in 2008, told Putin that the 3-week-old Russian bombing campaign had helped to stop the spread of "terrorism" in his country. In Putin's speech Thursday, Russian news agencies quoted Putin as saying that Syria's leaders "should establish working contacts with those opposition forces that are ready for dialogue." "As I understood from my conversation with President Assad the day before yesterday, he is ready for such a dialogue," Putin added. Kerry said Thursday the various powers with an interest in resolving Syria's conflict agree on "unified principles." He added: "One thing stands in the way of being able to rapidly move to implement that and it's a person called Assad, Bashar Assad." Kerry spoke alongside German Foreign Minister Frank-Walter Steinmeier, who said finding a road to a political solution "depends on whether Washington and Moscow find bridges to each other." Saudi Foreign Minister Adel al-Jubeir said ahead of Friday's meeting that Russia's actions in Syria are fueling the country's war, which can only be ended with Assad's unconditional exit. "We believe that the Russian interference in Syria is very dangerous because it exacerbates the conflict," Jubeir told reporters in Vienna, adding that the Saudis had made this clear to the Russians. "We believe that it will be viewed as Russia inserting itself in a sectarian conflict in the Middle East. We're concerned that this will trigger emotions in the Muslim world that will cause an increase in fighters to go to Syria." Almost 80 percent of Russia's declared targets in Syria have been in areas not held by ISIS, a Reuters analysis of Russian Defense Ministry data shows, undermining Moscow's assertions that its aim is to defeat the group. When asked whether Assad could play a role in any interim government Jubeir said: "His role would be to leave Syria. ... The best case scenario is that we wake up in the morning and Bashar Assad is not there."