The State Department did not immediately respond to a request for comment. The move by the chairmen, however, suggests the House is moving rapidly to advance its fledgling efforts to investigate and draw up articles of impeachment related to Trump's conduct toward Ukraine.

The House subpoena was accompanied by a schedule of depositions for senior State Department officials who have been identified as important players in the Ukraine episode — which was first brought to Congress' attention by an intelligence community whistleblower. The whistleblower, whose story was deemed "urgent" and "credible" by an agency watchdog, indicated that Trump had abused his power to pressure Ukrainian President Volodymyr Zelensky to help his reelection chances during a phone call -- and then the transcript of the call was inappropriately hidden on a highly classified server.

Trump, seeking to control the story, ordered the release of a summary of a July 25 call with Zelensky, which confirmed the thrust of the whistleblower's account.

Democrats intend to depose former U.S. ambassador to Ukraine Marie Yovanovitch — who was removed by Trump and criticized by the president in the call with Zelensky — U.S. ambassador Kurt Volker, who facilitated some of Giuliani's contacts with Ukrainian officials; deputy assistant secretary George Kent, Counselor T. Ulrich Brechbuhl and Ambassador Gordon Sondland. The depositions are set to take place between Oct. 2 and Oct. 10, while Congress is out on a two-week recess.

Democrats had been exploring Trump and Giuliani's posture toward Ukraine since June but sounded the alarm in early September, when the three chairmen launched a probe related to Giuliani and Trump's suggestion that Biden be investigated for his role in the ouster of a Ukrainian prosecutor who was seen by the international community as corrupt.

In a Sept. 9 letter to Pompeo, the Democrats asked for any State Department correspondence related to Trump's former campaign chairman Paul Manafort — whose business dealings in Ukraine helped land him in prison last year — records of Trump's July 25 call with Zelensky, a list of officials with knowledge of the call, records related to Giuliani and records related to an unexpected decision to suspend military aid to Ukraine, just days before Trump spoke to Zelensky about Biden.

