KIEV, Feb. 26 (Xinhua) -- Ukraine's President Petro Poroshenko discussed the situation in the Black Sea with Kurt Volker, the U.S. special envoy on Ukraine, the presidential press service said on Tuesday.

The talks were held at U.S. guided-missile destroyer USS Donald Cook that was making a call at the southern Ukrainian Black Sea port of Odessa, according to a statement posted on the presidential website.

During the talks, Poroshenko thanked the United States for sending the vessel to the Black Sea at the request of Ukraine, saying that it is a vivid demonstration of the level of cooperation between Kiev and Washington.

"We are grateful to our reliable ally. This is how we consider the development of our cooperation, inter alia, in the defense sphere," Poroshenko said.

The increased U.S. presence in the Black Sea is an important answer to the Kerch Strait incident, Poroshenko said.

For his part, Volker emphasized that the United States stands for the freedom of navigation and calls on the release of the Ukrainian seamen seized during the Kerch Strait incident.

In November, three Ukrainian ships and more than 20 sailors attempting to sail through the Kerch Strait from the Black Sea to the Sea of Azov were seized by Russian forces for allegedly violating the Russian border.

Moscow called the incident a "political provocation" staged by Ukraine, while Kiev accused Russia of "aggressive actions" and urged the North Atlantic Treaty Organization (NATO) to deploy ships in the Black Sea and the Sea of Azov over the incident.

On Feb. 25, USS Donald Cook arrived in Odessa for a three-day visit aimed at further strengthening the U.S.-Ukrainian partnership and supporting Ukraine.