US President Barack Obama has called for effective international monitoring of the ceasefire in Ukraine.<br /><br /> During a visit by EU Council President Donald Tusk to the White House, both men stressed a tough response to Russia was needed over its role in the crisis.<br /><br /> “We very much appreciate the work that has been done by Chancellor Angela Merkel and President François Hollande to establish a Minsk process, but we also know from experiences over the last year that unless we have strong monitoring and strong implementation that these agreements will be meaningless,” Obama told reporters.<br /><br /> “Our enemies who use propaganda against us commit acts of violence and violate the sovereignty of our neighbours,” Tusk said. <br /><br /> “And this is why, I think, united we stand, divided we fall. I’m convinced it’s true.”<br /><br /> With tension between the West and Russia at a post Cold War high, Obama is seeking support from his European allies to maintain pressure on the Kremlin.<br /><br /> Our correspondent in Washington, S
