Pentagon officials have announced the USS Vella Gulf, a US warship, will reach the Black Sea later this week as part of maneuvers showing support for Ukraine.

Navy Rear Admiral John Kirby was quoted by the Huffington Post as saying that the US also aimed to reassure its European allies that Washington is committed to their security, as tensions between Kiev and Moscow remain.

Kirby did not elaborate on the date when Vella Gulf, a guided missile cruiser, was expected to arrive, but Russia's ITAR-TASS reports this will happen on May 23, citing military sources.

The 172-meter-long warship USS Vella Gulf is equipped with Tomahawk cruise missiles, ASROC anti-submarine missiles and Standard-2 and Standard-3 surface-to-air missiles. It has two multi-purpose helicopters based on it.

It is the latest alliance vessel to have presence in the Black Sea over the past few months, after NATO pledged to boost military cooperation with its eastern members, including those having a Black Sea coastline, following Russia's absorption of Crimea.

Destroyers USS Truxtun and USS Donald Cook and frigate USS Taylor, as well as French anti-submarine frigate Dupleix and surveillance ship Dupuy de Lome were among the units which have been deployed in the basin since March this year. Some of them have held joint drills with Bulgarian and Romanian vessels.

NATO has also reconfirmed its sources have not observed a pullback of Russia's troops near the Ukrainian border, John Kirby also explained on Tuesday.

The alliance estimates soldiers along the western Russian borders number 40 000 people.

Most of them, in the Kremlin's words, were deployed there for large-scale military drills prompted by the situation in the neighboring Ukrainian Donetsk and Luhansk regions, where separatists have been occupying a number of public buildings, while Kiev forces have been carrying out an anti-terrorist operation to regain control.

On Monday, however, Moscow announced that Russian President Vladimir Putin has ordered that troops withdraw from temporary deployments as their exercise had ended.

This has been the third time when Russia announces its soldiers have left the border, with NATO denying every time that evidence of a massive pullback has been found.