The UN's Mideast envoy strongly urged Lebanon and Syria Friday to demarcate their borders and establish diplomatic relations as a way of reducing tensions between the two Arab neighbors. Speaking to reporters in Beirut, the envoy, Terje Roed-Larsen, said it was paramount for leaders of the two countries to agree on their shared borders - a reference to the disputed Chebaa Farms area on Lebanon's southern border. Lebanon claims Shaba Farms, which has been controlled by Israel since it captured the Golan Heights from Syria in the 1967 Arab-Israeli war, but the United Nations says Shaba is Syrian and that Syria and Israel should negotiate its fate. Syria says the farms are Lebanese, but has yet to present the UN with documents to back that claim. "It is urgent for representatives of the government of Syria and representatives of the government of Lebanon, to sit down and agree on that boundary," he said. The United Nations, he said, will lend all the support it can for such an exercise.