Ukrainian President Petro Poroshenko has had a telephone conversation with U.S. Secretary of State Mike Pompeo to discuss further measures to counteract Russian aggression and restoration of Ukraine's territorial integrity, the Ukrainian presidential press service said in the early hours on Wednesday.

"The parties commended approaches to further counteraction to Russian aggression and restoration of Ukraine's territorial integrity, taking into account recent contacts between the two Heads of State," the press service issued a statement posted on Poroshenko's official website.

Poroshenko thanked Pompeo for the "historic declaration of non-recognition of the attempt by the Russian aggressor to annex the Ukrainian Crimea." In this regard, the parties stressed the priority of switching from the policy of non-recognition of the annexation to the policy of ending the occupation of Crimea.

"It was noted that U.S. approaches towards policy regarding Russia remained clear and unambiguous – as long as the Kremlin refuses to change its confrontational policy, the price of aggression for Russia will continue to grow," the statement said.

The two officials emphasized that the policy of sanctions against Russia would be maintained until the restoration of sovereignty and territorial integrity of Ukraine, including Crimea.

"Attempts by the Russian side to aggravate the situation will further receive an adequate response and increase the price of the ongoing aggression," the statement said.

Poroshenko and Pompeo discussed the importance of coordinated actions in the promotion of the deployment of UN peacekeepers throughout Russian-occupied Donbas, including the return of control over the uncontrolled section of the Ukrainian-Russian border.

Poroshenko's press service said that significant attention had been paid to the issue of the release of the Ukrainian hostages and political prisoners kept in Russia and in the occupied territories of Donbas and Crimea.

"We must increase pressure on Russia to release all Ukrainian hostages as soon as possible, in particular Oleh Sentsov, who has been on a hunger strike for 86 days already," Poroshenko said.

Poroshenko and Pompeo confirmed the resolute position of Kyiv and Washington on the existing security challenges resulting from the Nord Stream 2 project.

The two officials also discussed important issues of strengthening strategic partnership between Ukraine and the United States, in particular in the field of security and defense. They also covered support for the progress of Kyiv on the path of reforms, including the development of cooperation with the International Monetary Fund.

Also, Pompeo hailed the "successful beginning of the process of launching the Anti-Corruption Court."