By Natalia Zinets KYIV (Reuters) – President Volodymyr Zelenskiy said Ukraine hoped to secure heavy weapons at talks with the U.S. secretaries of state and defence in Kyiv on Sunday, supplies that he said were vital for Ukraine to eventually retake Russian-occupied territory. The Ukrainian leader warned that Kyiv would quit talks with Moscow if Russia destroyed “our people” surrounded in the war-torn city of Mariupol or staged referendums to create more breakaway republics on newly-occupied Ukrainian soil. At one point in an emotional news conference, he said that he thought Russia could use a…