Blacklisting ships in the fleet would represent the first U.S. sanctions on Moscow since Trump returned to the White House in January.

The envoy, Steve Witkoff, passed along “signals” from President Trump, according to an aide to President Vladimir V. Putin. Mr. Witkoff was making his fifth visit to Russia this year.

President Donald Trump’s trusted foreign envoy Steve Witkoff met with Russian President Vladimir Putin on Wednesday, after the Kremlin requested that Witkoff visit in a last-ditch effort to avoid the punishing new sanctions Trump has threatened to impose this week,