US Secretary of State Mike Pompeo said Washington's support for Ukraine was unwavering during a delicate visit Friday to the country at the heart of the US impeachment process. After talks with Pompeo, Ukrainian President Volodymyr Zelensky said he appreciated US support, but stressed that Washington should be more involved in resolving his country's conflict with Moscow-backed separatists.

Ukraine is walking a careful line in its relations with the United States - keen to maintain American backing in the war but wary of being further entangled in US domestic politics. Pompeo is the most senior US official to visit Ukraine since the start of the impeachment process against US President Donald Trump, who is accused of withholding military aid to push Kiev into investigating his Democratic rival Joe Biden.

Pompeo said there could be no doubts about Washington's support for Ukraine, calling it "a bulwark between freedom and authoritarianism in eastern Europe". "The United States sees that the Ukrainian struggle for freedom, democracy and prosperity is a valiant one. Our commitment to support it will not waver," he said at a news conference with Zelensky.

Zelensky, who allegedly faced the pressure from Trump in a July 25 phone call, called on Washington to "be more actively involved in the peace process in eastern Ukraine" and to appoint a special representative on the conflict. "I do not believe that our warm and important relations have been influenced by the question of the impeachment," he said.

Zelensky said he was "ready to go tomorrow" to meet with Trump in Washington. Pompeo said no date had been set yet for a White House meeting. A senior State Department official told reporters that talks between Pompeo and Zelensky were "very focused on investment and infrastructure". "There was no talk of impeachment or any investigations," the official said.