KYIV (Reuters) -U.S. President Donald Trump's Ukraine envoy Keith Kellogg arrived in Kyiv on Monday to discuss security and sanctions against Russia, the head of the Ukrainian presidential administration said. "Defence, strengthening security, weapons, sanctions, protecting our people, strengthening cooperation between Ukraine and the United States — there are many topics to discuss," Andriy Yermak wrote on the Telegram messaging app. (Reporting by Anastasiia Malenko; Editing by Kevin Liffey)