(Reuters) - President Volodymyr Zelenskiy said in an interview published on Friday that if Ukraine does not get promised U.S. military aid blocked by disputes in Congress, its forces will have to retreat "in small steps"."If there is no U.S. support, it means that we have no air defence, no Patriot missiles, no jammers for electronic warfare, no 155-milimetre artillery rounds," Zelenskiy told the Washington Post."It means we will go back, retreat, step by step, in small steps," he said. "We are trying to find some way not to retreat."Shortages of munitions, he said, meant "you have to do with...