The U.S. House of Representatives will vote this week on a resolution intended to affirm an impeachment inquiry against President Donald Trump as well as relevant procedures, Speaker Nancy Pelosi said on Monday.

"This week, we will bring a resolution to the Floor that affirms the ongoing, existing investigation that is currently being conducted by our committees as part of this impeachment inquiry, including all requests for documents, subpoenas for records and testimony, and any other investigative steps previously taken or to be taken as part of this investigation," Pelosi wrote in a letter to other House Democrats.

The California Democrat said that they are "taking this step to eliminate any doubt as to whether the Trump Administration may withhold documents, prevent witness testimony, disregard duly authorized subpoenas, or continue obstructing the House of Representatives."

The text of the resolution has yet to be released but the resolution will reportedly hit the House floor on Thursday.

White House press secretary Stephanie Grisham said in a statement that they "won't be able to comment fully until we see the actual text" while accusing Democrats of "conducting an unauthorized impeachment proceeding, refusing to give the President due process."

"Their secret, shady, closed door depositions are completely and irreversibly illegitimate," she added.

The impeachment inquiry into Trump was initiated last month by Pelosi after an anonymous whistleblower had raised concern about the president's interactions with Ukraine.

Trump was alleged to have abused power by using a military aid that Congress approved to pressure Ukrainian President Volodymyr Zelensky into investigating former U.S. Vice President Joe Biden, the leading 2020 Democratic presidential candidate, so as to help his re-election campaign.

The White House has said it will not provide documents or witnesses to House investigators because it considered the impeachment inquiry unfair and illegitimate.

Democrats have argued that there is no need to hold a full House vote to authorize the inquiry, citing Constitution stating that the lower chamber "shall have the sole Power of Impeachment."

Trump has denied any wrongdoing and has urged more efforts from Republicans to defend him and challenge the impeachment inquiry, as depositions are turning to the White House and a series of witnesses have testified behind closed doors before House panels leading the investigation.