The United States has suspended military cooperation with Russia due to its military intervention in Ukraine.
US Secretary of State John Kerry prepared to visit Kiev Tuesday amid a deepening crisis.
“We have, in light of recent events in Ukraine, put on hold all military-to-military engagements between the United States and Russia,” Pentagon spokesman Rear Admiral John Kirby said in a statement Monday.
The suspension of the post-Cold War cooperation covers exercises, bilateral meetings, port visits and planning conferences, Kirby added.
The crisis now threatens to blow up into the biggest test for global diplomacy -- and relations between Moscow and the West -- since the fall of the Berlin Wall in 1989.
Kirby stressed that the suspended system had been “developed over the past few years to increase transparency, build understanding, and reduce the risk of military miscalculation.”
Both Washington and the European Union said they were looking at a range of sanctions against Russia for its threat to use force against an ex-Soviet neighbour for the first time since a brief 2008 conflict with Georgia.
The West's warnings to Moscow came shortly after Ukrainian defence officials on the flashpoint Crimean peninsula said Russia had given its forces an ultimatum to surrender or face an all-out assault.
“The ultimatum is to recognise the new Crimean authorities, lay down our weapons and leave, or be ready for an assault,” regional Ukrainian defence ministry spokesman Vladyslav Seleznyov said.
But a spokesman for the Russian Black Sea fleet based in Crimea told the Interfax news agency the claim was “complete nonsense”.
