US Vice President Mike Pence talks to the gathered employees of Caterpillar during a visit to the Tinaja Hills Demonstrations and Learning Center, Green Valley, Ariz., Thursday, Oct. 3, 2019. (Photo: AP)

WASHINGTON, Oct. 4 (Xinhua) -- Three US House committees investigating President Donald Trump's alleged inappropriate interactions with Ukraine sent a letter on Friday to Vice President Mike Pence, notifying him to submit documents related to the matter.

"Pursuant to the House of Representatives' impeachment inquiry, we are hereby requesting that you produce the documents set forth in the accompanying schedule by October 15, 2019," read the letter sent by House Intelligence Committee Chairman Adam Schiff, Foreign Affairs Committee Chairman Eliot Engel and Oversight and Reform Committee Chairman Elijah Cummings.

The action is part of the ongoing impeachment inquiry into Trump stemming from a whistleblower complaint alleging that the president pressured his Ukrainian counterpart, Volodymyr Zelensky, during a July 25 phone call to investigate Joe Biden, Democratic presidential candidate for the 2020 election, as well as issues related to alleged Russian interference in the 2016 election.

The chairmen cited "recent public reports" as saying Pence may have played a role "in conveying or reinforcing the President's stark message to the Ukrainian President."

"Your failure or refusal to comply with the request, including at the direction or behest of the President or the White House, shall constitute evidence of obstruction of justice of the House's impeachment inquiry and may be used as an adverse inference against you and the President," the chairmen warned Pence in the letter.

The committees requested from Pence all documents and communications related to Trump's April 21 and July 25 phone calls with Zelensky.

They also asked Pence to hand in records on meetings with former US Special Representative for Ukraine Negotiations Kurt Volker, who resigned on Sept. 27 under pressure from Congress, as well as with US Ambassador to the European Union Gordon Sondland and Ukrainian officials.

Volker testified behind closed doors Thursday before House lawmakers, during which he provided text messages involving Trump administration officials -- including Volker himself and Sondland -- and Ukrainian officials. The messages revealed the extent to which the Trump administration pressured Ukraine before and after the July 25 presidential phone call.

Furthermore, the panels asked Pence for documents related to his own call with Zelensky on Sept. 18, and anything he knew about Washington withholding military aid from Kiev.