DUBAI (Reuters) -There's an unprecedented deadlock at this year's COP28 U.N. climate summit over who will host next year's event. Under U.N. rules, it is the turn of eastern Europe to host a COP, and the decision must be unanimous by all countries in the region. Russia, which is being sanctioned by the European Union for invading Ukraine, has opposed holding COP29 in an EU member state and is blocking Bulgaria's bid.