WARSAW, March 15 (Reuters) - An international peacekeeping mission should be sent to operate in Ukraine, the leader of Poland's ruling party said on Tuesday during a press conference in Kyiv alongside Ukrainian President Volodymyr Zelenskiy. "I think that it is necessary to have a peace mission - NATO, possibly some wider international structure - but a mission that will be able to defend itself, which will operate on Ukrainian territory," Jaroslaw Kaczynski said during the conference, which was broadcast on Polish television.