By Bassem Mroue and Ian Phillips Associated Press BEIRUT – President Bashar Assad’s government came under mounting international pressure after a chemical attack in northern Syria, with even key ally Russia saying its support is not unconditional and the U.S. launching a barrage of cruise missiles at a government-controlled air base in Syria. Turkey, meanwhile, said samples from victims of Tuesday’s attack, which killed more than 80 people in the town of Khan Sheikhoun, indicate they were exposed to sarin, a highly toxic nerve agent. Syria rejected the accusations, and Moscow warned against apportioning blame until an investigation has been carried out. Kremlin spokesman Dmitry Peskov said in an interview with The Associated Press on Thursday that “unconditional support is not possible in this current world.” But he added that “it is not correct to say that Moscow can convince Mr.