The US Pentagon is sending additional 175 marines to Romania in an effort to strengthen its force of more than 300 marines already deployed in the country.

The United States is deploying additional marines to enlarge a rotational crisis response force based in Spain, and is also dispatching a naval vessel to the Black Sea to conduct exercises with US allies in the region, according to the official web site for the US Department of Defense.

The expeditionary force falls under US Africa Command but can be deployed anywhere. It enables the United States to conduct a range of military operations including non-combatant evacuations, humanitarian assistance and disaster relief as well as support for US embassies.

While the additional Marines will be part of the Spain-based force, they are being stationed in Romania to allow greater flexibility. They will join nearly 300 marines already in the country who are part of the Black Sea rotational force.

A Pentagon spokesman emphasized the decision to send the additional Marines to Romania is not related to developments in Ukraine.

The US announced it is sending a second destroyer into the Black Sea as a gesture of support for Ukraine and other allies. The Pentagon has confirmed that the unit is heading to the sea, without specifying the date of its arrival.