Secretary of State Marco Rubio will not attend the NATO meeting, with Deputy Secretary of State Christopher Landau representing the U.S. instead, raising concern among allies over the U.S. commitment after President Donald Trump's controversial peace plan for Ukraine.NATO Secretary-General Mark Rutte explained Rubio's absence as due to scheduling and reaffirmed Ukraine's path to membership, as Landau urged NATO members to raise defense spending.Steve Witkoff and Jared Kushner held talks with Russian President Vladimir Putin in Moscow to discuss a revised peace plan, while former NATO Secretary General Anders Fogh Rasmussen and military expert Claus Mathiesen warned that Donald Trump's approach could threaten NATO's cohesion.