House Democrats subpoenaed US Secretary of State Mike Pompeo for Ukraine-related documents on Friday as they plunged into an impeachment probe of President Donald Trump.

The heads of three House committees gave Pompeo one week to produce the documents, saying a number of State Department officials have direct knowledge of Trump’s efforts to enlist the Ukraine government’s help in his domestic political campaign for reelection.

“The Committees are investigating the extent to which President Trump jeopardized national security by pressing Ukraine to interfere with our 2020 election and by withholding security assistance provided by Congress to help Ukraine counter Russian aggression,” they said.

“The subpoenaed documents shall be part of the impeachment inquiry and shared among the Committees. Your failure or refusal to comply with the subpoena shall constitute evidence of obstruction of the House’s impeachment inquiry,” they wrote.

The subpoena came one day after the release of an intelligence official’s bombshell whistleblower complaint that describes Trump pressuring Ukraine’s President Volodymyr Zelensky in a July 25 phone call to supply dirt on Democratic political rival Joe Biden.

The complaint also describes the involvement of Trump’s private lawyer Rudy Giuliani, who allegedly worked with several US diplomats to pressure Zelensky to help Trump by investigating Biden.

Biden, the former US vice president, is the Democratic frontrunner to battle Trump in next year’s presidential election.

“It has become clear that multiple State Department officials have direct knowledge of the subject matters of the House’s impeachment inquiry,” the subpoena said.

The committees also told Pompeo they planned to depose five State Department officials in the next two weeks.

They include former ambassador to Ukraine Masha Yovanovitch, whom Trump reportedly forced out earlier this year for resisting his and Giuliani’s efforts to pressure Kiev to probe Biden. (AFP)