US Democrats issued a subpoena to Secretary of State Mike Pompeo on Friday, compelling him to turn over documents related to President Donald Trump's dealings with Ukraine.

The subpoena was issued by the Committee on Foreign Affairs in consultation with two other committees conducting a preliminary impeachment inquiry.

"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," the subpoena read.

The subpoena also warned that Pompeo's refusal or failure to produce the documents would be considered evidence of "obstruction of the House's impeachment inquiry."

Surprise resignation

Following the announcement of the subpoena, US special envoy to Ukraine Kurt Volker resigned, US media outlets reported.

The House Intelligence, Foreign Affairs and Oversight Committees plan to depose Volker along with other State Department officials about Trump's call with the Ukrainian president.

A whistleblower complaint alleges that Volker was in contact with Trump's lawyer Rudy Giuliani to try to "contain the damage" from the president's efforts to pressure the Ukrainian government into investigating his democratic political rival.

First steps towards impeachment

Over the past few weeks, Democrats have repeatedly asked the State Department to hand over documents related to the Trump administration's relationship with Ukraine. The committees gave Pompeo an October 4 deadline to produce the documents.

Although impeachment hearings have yet to formally begin, House Democrats have begun a preliminary inquiry.

Read more: Opinion: Ukraine's Zelenskiy is a servant of Donald Trump

"We will move as expeditiously as possible," Intelligence Committee head Adam Schiff told CNN. "But we have to see what witnesses are going to make themselves available and what witnesses are going to require compulsion."

The committees announced the subpoenas after the Trump administration missed a deadline Thursday to turn over documents and information about contacts with Ukrainian officials.

The subpoena also said Pompeo's refusal to provide documentation on Ukraine was "impairing Congress' ability to fulfill its constitutional responsibilities to protect our national security and the integrity of our democracy."

The House Foreign Affairs, Intelligence and Oversight Committees also scheduled depositions for other State Department officials over the next two weeks, including former US Ambassador to Ukraine Marie Yovanovitch and US Ambassador to the EU Gordon Sondland.

Details of Russia meeting emerge

The Washington Post reported on Friday that the Trump administration had previously attempted to quash details of a 2017 meeting in which Trump reportedly told Russian diplomats that he was unconcerned over Moscow's alleged interference in the 2016 election.

A briefing of the president's meeting with Russia's foreign minister and its ambassador was kept to a few officials in an effort to prevent Trump's comments from being made public, the report said, citing former officials.

Meanwhile, CNN reported a similar pattern of behavior after phone calls with Saudi Crown Prince Mohammed bin Salman and Russian President Vladimir Putin, in which details were kept unusually secret.

Watch video 01:56 Share US lawmakers probe whistleblower report on Trump Send Facebook google+ Whatsapp Tumblr linkedin stumble Digg reddit Newsvine Permalink https://p.dw.com/p/3QJS2 US lawmakers probe whistleblower report on Trump

wmr, kp, jsi/aw (Reuters, AFP)

Every day, DW's editors send out a selection of the day's hard news and quality feature journalism. You can sign up to receive it directly here.