As it tries to demonstrate its continuing ability to fight, Ukraine said it had used drones to inflict serious damage on a Russian Kilo-class submarine at a Black Sea port.

The officials said that robust negotiations between President Trump’s envoys, Steve Witkoff and Jared Kushner, and Ukrainian President Volodymyr Zelensky and his team led to progress on narrowing differences on security guarantees Kyiv said must be provided.