Syria's President Bashar Assad said Sunday that the air campaign by Russia against "terrorists" in his country must succeed or the whole region will be destroyed, stressing that the fight against terrorism must precede a political process. In the interview with Iran's Khabar TV, Assad also accused Western nations of fueling the refugee crisis and said the U.S.-led coalition to fight ISIS will only spark more instability in his country and the region. These were Assad's first comments since Russia launched its air campaign against multiple armed groups in Syria Wednesday. While ISIS controls large parts of eastern Syria, the Russian attacks have largely focused on the northwestern and central provinces – the gateways to the heartland of Assad's power in the capital and on the Mediterranean coast. Assad said the Russian campaign has the potential to succeed because it is supported by Iran and has international, if not Western, support. He called on countries that support the armed opposition to stop, which would increase the chances of the campaign to succeed. "It must succeed or we are facing the destruction of a whole region, and not a country or two," he said. "The chances for success are large, not small." Assad has accused Western countries, neighboring Turkey and some Gulf states of fueling the war by supporting the armed opposition, all of which he calls terrorists. Militant groups ISIS and Al-Qaeda's affiliate in Syria, the Nusra Front, are among the strongest groups operating in Syria. But there are dozens of other rebel groups, some western-backed and armed, fighting against Assad and ISIS.Assad said combatting terrorism is "the basis for any solution in Syria." "The only solution for us is to strike at terrorism. Implementing any solution or political ideas agreed upon will need a state of stability. Otherwise it will have no value," he said. Russian intervention in the past week has drawn the criticism of Western powers invested in Syria. British Prime Minister David Cameron said Sunday that Kremlin chief Vladimir Putin's decision to take military action in Syria to support Syrian President Bashar Assad was a "terrible mistake." "They are backing the butcher Assad, which is a terrible mistake for them and for the world," Cameron told the BBC. "It's going to make the region more unstable, it will lead to further radicalization and increased terrorism. I would say to them ‘change direction, join us in attacking ISIS.'" Erdogan echoed Cameron's words at a news conference in Turkey, Hurriyet Daily News reported. "Russia is at the moment making a grave mistake. This may be a sign of a step that will take it to loneliness in the region." The British leader added that Britain will get 20 more Predator drones and strengthen its special forces to help quell the growth of ISIS in Syria and Iraq. French Prime Minister Manuel Valls urged Russia Sunday to direct air strikes at ISIS militants alone in Syria. Valls said Russia should not "get the wrong targets," echoing the words of French President Francois Hollande to Putin at a Paris summit Friday. Valls also called on Russia to spare civilian lives, hitting out at Assad's sanctioning of the use of destructive weapons against his own population. German Chancellor Angela Merkel said Sunday that "military efforts" were needed in Syria but they would not be enough to end four years of bloodshed. Merkel urged talks with all sides in the conflict, in an interview with public broadcaster Deutschlandradio. "We need a political process, which has had difficulties getting under way ... [To] achieve a political solution, I need representatives of the Syrian opposition as well as representatives of those in power at the moment in Damascus and others, and above all the allies of the various groups, to achieve real success." Israeli Prime Minister Benjamin Netanyahu said Israel wants to avoid an adversarial relationship with Moscow and is unsure how Russia's recent military intervention in Syria will affect the situation there. "We don't want to go back to the days when, you know, Russia and Israel were in an adversarial position," said Netanyahu, who met with Putin in Moscow late last month. "I think we've changed the relationship. And it's, on the whole, good." Egypt's Foreign Minister Sameh Shoukri, in a change of tone, said on Saturday Russia's intervention curtails the spread of terrorism and helps deal a fatal blow to ISIS.