Kurt Volker, the Unites States special representative on Ukraine who got caught in the middle of a whistle-blower complaint over President Donald Trump's dealings with Ukraine, has resigned, according to a US official, Al Jazeera reports.
Volker's departure is the first since the emergence of reports that Trump may have abused his presidential powers and sought help from a foreign government to undermine former Vice President Joe Biden, the current Democratic frontrunner, and help his own re-election.
The disclosures have prompted an impeachment inquiry, and Congress on Friday ordered Volker to answer questions in the investigation next week.
The official was quoted as saying by The Associated Press news agency that Volker told Secretary of State Mike Pompeo on Friday of his decision to leave the job, following disclosures that he had connected Trump's personal lawyer Rudy Giuliani with Ukrainian officials to investigate Biden and his family over alleged corrupt business dealings.
Giuliani has said he was in frequent contact with Volker about his efforts.
The State Department had no immediate comment on his resignation and has only said that Volker put Giuliani in touch with an aide to Ukraine's president.