"Russia has a history of taking aggressive actions against Ukrainian vessels and impeding international maritime transit in the Black Sea, particularly near the Kerch Strait. This would be the latest example of its ongoing campaign to undermine and destabilize Ukraine," Pentagon spokesman John Kirby told reporters at a news conference.
Russia's plan to temporarily restrict movement of foreign warships in part of the Black Sea will not affect the nearby Kerch Strait, the RIA news agency reported, signalling lower risks for regional trade from Russia-Ukraine tensions.
The Kerch Strait is a crucial part of the regional grain trade connecting the Azov sea with the Black Sea. The area is also close to military drills which Moscow and Kyiv held simultaneously this week.
The right of passage of foreign warships and "other state ships" will be suspended in three spots near Crimea's Black Sea coast from April 24 until October 31, RIA said, citing Russia's defence ministry.
Moscow annexed the Crimean peninsula from Ukraine in 2014.
But the planned restrictions will not affect navigation in the Kerch Strait or its entry points, RIA said.
The Ukrainian foreign ministry said that Russia's actions to close off parts of the Black Sea to foreign warships were illegal.