The head of the United Nation's refugee agency said on Tuesday it must be ready in case Ukraine's crisis causes refugees to flee Crimea, but his biggest worry is that "a total disaster" could occur if the international community diverts its attention away from Syria's conflict.Antonio Guterres, the head of the UN's High Commission for Refugees (UNHCR), said in an interview that little progress was being made in efforts by the United States and Russia, now at loggerheads over Ukraine, to bring Syria's warring sides together after the collapse of talks in Geneva last month. "In the moment in which we need the most relevant countries in the world to be able to come together to narrow their differences and to try to find a way to move into peace for Syria, this tension around Ukraine will obviously not help," Guterres told Reuters while visiting Washington to discuss Syria's refugee crisis."I hope that those that have the most important responsibility in world affairs will be able to understand that forgetting Syria will be a total disaster," he said.Tensions between Washington and Moscow have risen over Russia's bloodless seizure of Ukraine's Crimea region, which has brought US-Russian relations to one of their lowest points since the Cold War.The United States and European allies have threatened sanctions against Moscow, which has said people in Crimea, a small majority of whom are ethnic Russians, should have the right to secede by voting in a referendum to be held on Sunday.Guterres said his agency was preparing for the possibility of refugees from Crimea and had moved teams inside Ukraine to monitor the situation."We are preparing ourselves for any movement of population that might occur," said Guterres. "Until now it has not happened in a significant way, and we hope that it will be avoided," he said."Our hope is that things will not evolve in a way that will force large numbers of people to be displaced. We have enough problems of refugees and displaced people in the world, we can live without a new massive displacement," he added.But Guterres said he was concerned that tensions between Russia and the West over Ukraine could worsen divides that have already played out in the UN Security Council over Syria. Throughout the civil war, Russia, backed by China, has shielded Syria on the UN Security Council by vetoing three resolutions condemning Syria's government and threatening it with possible sanctions."I don't think there are reasons to be optimistic," he said of the possibility of resolving the Syrian war."We see the war going on and on and on, not only with tragic humanitarian consequences with suffering of Syrian people that is unimaginable, but also becoming a serious threat to global peace and security, not only to regional stability but also to global peace and security."Repeating what political leaders have said that the conflict can only be resolved through political dialogue, Guterres also said that "discreet diplomacy" was needed among the main players - the US, Saudi Arabia, Russia and Iran - to narrow differences and avoid a prolonged deadlock in talks."There was never any major international crisis that was solved without a lot of silent, discreet diplomacy behind the scenes to support the public diplomacy process," he said. "That is lacking in the Syrian crisis."With the Syrian conflict now heading toward a fourth year this week and more people fleeing the war, the UN has warned that Syrians are about to replace Afghans as the world's largest refugee population.There are currently more than 2.5 million Syrian registered by the UN in neighboring countries such as Lebanon, Turkey, Jordan and Iraq, but Guterres said it is believed more than 3 million have fled the conflict."It is absolutely essential that the international community mobilizes massively to support Lebanon, to support Jordan, to support all the other neighboring countries to make sure that they are able to cope with the challenge and to preserve the stability of the region," he said.