MARIUPOL • Ukrainian officials will not testify in the US Congress in the impeachment inquiry into President Donald Trump because Kiev does not want to get involved in the internal affairs of another country, Ukraine's Foreign Minister said.

"We don't have anything to do with this at all," Mr Vadym Prystaiko told reporters on Tuesday, on the sidelines of an investment conference in Mariupol.

"We won't go there, we won't comment," he added.

Democrats are investigating whether there are grounds to impeach Mr Trump over his request to Ukrainian President Volodymyr Zelensky to investigate a domestic political rival, former vice-president Joe Biden.

Mr Biden is a front runner for next year's Democratic presidential nomination.

The top United States diplomat in Ukraine, Mr William Taylor, has testified that Mr Trump made the release of US security aid to Ukraine contingent on Kiev publicly declaring that it would carry out investigations that Mr Trump sought.

Mr Trump has called the inquiry a witch hunt.

He has said there was no quid pro quo related to the US$391 million (S$533 million) aid package to help Ukraine fight Russia-backed forces in the eastern Donbass region.

Mr Prystaiko said relations between Kiev and Washington had not changed since the start of the impeachment row.

"There are channels that are specially separated from the official ones, but this does not mean that the official ones don't know what is happening," he said.

He also said that Ukraine needed to receive official requests from the US in order to open investigations.

Asked whether Ukraine had received such a request to investigate Burisma, the Ukrainian gas company where Mr Biden's son Hunter used to be a board member, he said that question should go to the General Prosecutor's office.

REUTERS