WASHINGTON (Reuters) – There will be no meeting between U.S. President Donald Trump and Russian President Vladimir Putin while Russia still holds Ukrainian ships and sailors seized near Crimea, U.S. national security adviser John Bolton said on Thursday.

“I don’t see circumstances in the foreseeable future where such a meeting could take place until the ships and the crews are released,” Bolton told reporters at a Washington think tank.

Russia seized three Ukrainian navy vessels and their combined crew of 24 last month off the coast of Russian-annexed Crimea and accused them of illegally entering Russian waters.

Ukraine has said Russia captured the two small gunboats and one tugboat illegally and accused Moscow of military aggression.

Two Ukrainian navy captains being held in a Russian jail have refused to provide testimony because they consider themselves prisoners of war, their lawyers said.

(Reporting by Steve Holland and Doina Chiacu; Editing by Chizu Nomiyama and Jonathan Oatis)