By Erin Banco, Gram Slattery and Humeyra Pamuk WASHINGTON/RIYADH/ANTALYA, Turkey (Reuters) -U.S. President Donald Trump's senior envoys Steve Witkoff and Keith Kellogg will travel to Istanbul for potential talks on Thursday on how to end the war in Ukraine,

U.S. Secretary of State Marco Rubio and his NATO counterparts meet in Turkey to prepare a pivotal summit of alliance leaders next month that will set the course for future European security as America focuses on challenges elsewhere.

Russian President Vladimir Putin will not travel to Turkey for peace talks on the war in Ukraine, despite calls from Ukraine's Volodymyr Zelensky for him to attend.Russia's delegation at Thursday's talks in Istanbul will instead be headed by presidential aide Vladimir Medinksy,