What is Keith Kellogg's mission in Ukraine regarding security guarantees?

American envoy Keith Kellogg has arrived in Kyiv by train to meet with President Zelensky to discuss security guarantees for Ukraine. Upon his arrival, Kellogg emphasized his understanding of the importance of these guarantees for Ukraine's future safety. He specifically highlighted the need for military presence to prevent Russia from invading Ukraine again after any potential ceasefire agreement. This mission demonstrates American engagement in developing long-term security solutions to protect Ukraine's sovereignty once hostilities eventually end.