Ukraine’s domestic security service, the SBU, said Monday that it struck a Russian submarine in the Black Sea port of Novorossiysk, causing critical damage to the vessel and effectively disabling it.

President Donald Trump on Monday described an end to the war in Ukraine as closer than ever, with American officials earlier in the day suggesting beefed-up security guarantees for Kyiv had advanced the peace talks — but that the US offer would not be on the table forever.