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.

The Russian president faced pressure from Ukraine's Volodymyr Zelensky to travel for the talks in Istanbul on Thrusday.