The Black Sea naval confrontation between Russia and Ukraine and the fate of a major Cold War missile treaty will top the agenda for foreign ministers and diplomats from 29 NATO members meeting in Brussels.
Ahead of the December 4 meeting, NATO Secretary-General Jens Stoltenberg demanded that Russia release Ukrainian sailors and naval vessels it seized in the confrontation nine days ago near Crimea.
"There is no justification for this use of force. We call for calm and restraint. Russia must release the Ukrainian sailors and ships," Stoltenberg said on the eve of a two-day meeting of NATO foreign ministers.
Russia has been holding the sailors -- crewmen from three Ukrainian naval craft -- since the confrontation, which added to tension over Crimea, which Russia annexed in 2014.
U.S. officials, meanwhile, are expected to try and rally support for their contention that Russia violated the 1987 Intermediate-Range Nuclear Forces Treaty by testing and then deploying a missile banned under the treaty, known as the INF.
U.S. officials have been sharing with European allies more detailed intelligence on the missile, and Director of National Intelligence Dan Coats last week for the first time provided specific indications of how Russia allegedly tested it.
Moscow has repeatedly denied any violation, though after years of denials, it has acknowledged the existence of the missile that Washington has identified.
President Donald Trump in October announced that the United States would be withdrawing from the INF.
The alliance will also host an expanded meeting of its governing North Atlantic Council to involve foreign ministers from Georgia and Ukraine. Russia has vehemently opposed any efforts by NATO to admit former Soviet states into the alliance.