The US President's special representative for Ukraine has reportedly resigned from his posting.
CNN understands Kurt Volker walked away from the role after he was named in a whistleblower complaint surround Donald Trump's correspondence with the Ukrainian president.
It comes as three US House of Representatives committees have jointly issued a subpoena to Secretary of State Mike Pompeo for documents related to the impeachment inquiry against President Trump.
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The chairmen of the House Foreign Affairs, Intelligence and Oversight committees have set an October 4 deadline for Pompeo to produce the documents, including many that the lawmakers have been seeking for weeks.
The committees are investigating Trump's actions in repeatedly pressing Ukraine leaders to investigate former vice president Joe Biden and his son.
Democrats say Trump interfered with the 2020 election and risked national security, and are pursuing his impeachment.
The committees also sent a separate letter notifying Pompeo that they have scheduled depositions for five State Department officials over the next two weeks, including former ambassadors Marie "Masha" Yovanovitch and Kurt Volker.
