House Democrats on Friday sent a letter requesting documents from Vice President Mike Pence as part of the impeachment inquiry into President Trump’s July call with his Ukrainian counterpart.

Democrats on the House Intelligence, Foreign Affairs and Oversight and Reform Committees sent the letter requesting documents related to the impeachment inquiry by Oct. 15.

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That inquiry is looking into whether Trump pressured Ukraine to interfere in the 2020 election by freezing Ukraine military aid, then urging President Volodymyr Zelensky to investigate former Vice President Joe Biden, his son Hunter and their business dealings in Zelensky's country. Democrats have claimed that the call revealed a quid pro quo in which Trump tied the request to nearly $400 million in frozen military money.

Pence spokesperson Katie Waldman said late Friday that the vice president's office received the letter "after it was released to the media and it has been forwarded to [White House] Counsel’s Office for a response.

"Given the scope, it does not appear to be a serious request but just another attempt by the Do Nothing Democrats to call attention to their partisan impeachment," Waldman added. "Despite their efforts to distract and obstruct our agenda, this Administration will stay focused on creating jobs, securing the border, rebuilding our military, negotiating better trade deals, and the issues most important to the American people."

The letter to Pence points to recent reports that it says raise questions about Pence’s role in doubling down on Trump’s message to Zelensky -- including a Sept. 1. meeting with Zelensky in Warsaw.

Specifically, it cites a Washington Post article that reported Pence was involved in efforts to exert pressure on Ukraine, including telling Zelensky that U.S. aid was being withheld while also demanding more action on corruption. Officials close to Pence told The Post that he was unaware of Trump’s discussion about Biden, although it also reported that a member of Pence’s staff may have participated in the July call.

“Recently, public reports have raised questions about any role you may have played in conveying or reinforcing the president’s stark message to the Ukrainian president,” the letter says. “The reports include specific references to a member of your staff who may have participated directly in the July 25, 2019, call, documents you may have obtained or reviewed, including the record of the call, and your Sept.1, 2019, meeting with the Ukrainian president in Warsaw, during which you reportedly discussed the administration’s hold on U.S. security assistance to Ukraine.”

The documents the committees are requesting include all those related to Trump’s call in July, and another in April, as well as communications among current or former officials and meetings between Trump officials and Ukrainian government officials. Trump has previously said that Democrats can have the transcript of the April call.

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The move represents the latest salvo in the escalating impeachment war between the White House and House Democrats. Democrats have been preparing subpoenas for the White House, and Secretary of State Mike Pompeo faces a deadline to comply with a separate subpoena.

On Friday, Trump confirmed that he planned to send a letter to House Speaker Nancy Pelosi, D-Calif., “daring” her to hold a vote on Democrats’ impeachment inquiry. The letter is expected to say that the White House won’t comply with the Democrats’ investigation because Pelosi has not codified the probe with a formal vote on the House floor.

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He also defended his actions and sought again to put the spotlight back on Biden and alleged corruption in Ukraine.

“I don’t care about Biden’s campaign, but I do care about corruption,” Trump said. “I don’t care about politics, I don’t care about anything. I care about corruption.”

Fox News’ Brooke Singman and John Roberts contributed to this report.