North Korean leader Kim Jong Un may travel to Russia for a summit with President Vladimir Putin, a U.S. official said, in a trip that would underscore deepening cooperation as the two isolated leaders are locked in separate confrontations with the U.S. U.S. officials also said that Russia is seeking to buy ammunition from North Korea to refill reserves drained by its war in Ukraine. In return, experts said, North Korea will likely want food and energy shipments and transfers of sophisticated weapons technologies. A meeting with Putin would be Kim’s first summit with a foreign leader since North Korea…