By Sabine Siebold and John Chalmers BRUSSELS (Reuters) -EU leaders on Monday made clear they would fail to agree on a Russian oil import ban at a summit in Brussels, prompting swift criticism from Ukrainian President Volodymyr Zelenskiy who chastised them for being too soft on Moscow. The European Union has rolled out five packages of sanctions since Russia invaded Ukraine more than three months ago, demonstrating uncharacteristic speed and unity given the complexity of the measures. But the lack of agreement on a sixth package – and in particular on an oil ban – exposed a struggle to widen sa…