U.S. Ambassador to the United Nations Linda Thomas-Greenfield talks about the United Nations’ role in the Russia-Ukraine conflict. Richard Engel reports from Ukraine, Keir Simmons reports from Moscow and Kelly Cobiella from Poland. Sen. Mark Warner (D-Va.) and Sen. Rob Portman (R-Ohio) talk with Chuck Todd in an exclusive joint interview. Kori Schake, Clint Watts, Michael McFaul, Andrea Mitchell, Jeremy Bash, Danielle Pletka and Kristen Welker join the Meet the Press roundtables.