WASHINGTON — The White House is planning to spurn Democrats' request for documents sought as part of their impeachment inquiry as administration aides scramble to calibrate a legal response strategy.

White House lawyers plan to argue that until there is a formal vote by the House to begin impeachment proceedings, Congress doesn’t have the right to the information, people familiar with the discussions said.

“Well, we’ll be issuing a letter," President Donald Trump told reporters as he departed the White House on Friday. Asked whether he was going to cooperate with any House subpoenas, Trump was noncommittal.

"I don't know, that's up to the lawyers," he said. "I know the lawyers think they've never seen anything so unfair, never seen anything so unjust."

Trump had said Thursday he would leave the decision up to the lawyers on whether to cooperate with the congressional investigation into whether he used the power of his office to pressure Ukraine to investigate 2020 rival Joe Biden.

House Democrats have said they would subpoena White House officials by Friday if their demands were not met. Democrats said the panels would not consider contempt or any other penalties for noncompliance, and that White House failure to produce the documents would instead be used as evidence of obstruction for impeachment.

It was unclear what the White House was basing its legal argument on; the congressional rules manual leaders typically follow makes no mention of a vote being required, and there is no constitutional requirement for such an action. A White House spokesman declined to comment.

While Democrats in Congress have said in the past a formal vote would be needed to initiate an impeachment probe, they have denied in recent days that it is a prerequisite for the White House to have to comply with their inquiry.

Even without White House cooperation, Democrats have been amassing a growing body of evidence related to their case.

Congressional investigators uncovered text messages that show U.S. diplomats pressuring Ukraine to commit in public to investigating Biden and his son, Hunter, and linking that inquiry to a potential White House visit by Ukraine’s president.

The two ambassadors, both Trump picks, went so far as to draft language for what Ukrainian President Volodymyr Zelenskiy should say, the texts indicate. Text messages released by Congress overnight show U.S. ambassadors working to persuade Ukraine to publicly commit to investigating Trump’s political opponents and explicitly linking that inquiry to the question of whether Ukraine’s president would be granted an official White House visit.

The messages, released Thursday by House Democrats conducting the impeachment inquiry, show the ambassadors coordinating with both Trump's personal attorney Rudy Giuliani and a top Zelenskiy aide.

Full coverage: Trump impeachment inquiry

The Department of Defense announced Thursday that its general counsel had directed all DOD offices to produce information requested by Democrats dealing with the delayed military funding for Ukraine.

Acting White House chief of staff Mick Mulvaney and the president’s son-in-law Jared Kushner are trying to take the lead on the staff response to impeachment, creating a streamlined nonpresidential response process, coordinating across government agencies and taking into account actions by the state and defense departments, according to one official.

Aides and advisers to Trump have met throughout the week to craft their strategy even as the president made statements that shifted the parameters of the impeachment inquiry in unexpected ways.

On Thursday, Trump threw a new wrinkle into the impeachment probe when he publicly called on the Chinese to investigate Biden amid tense trade talks between the two countries.

Then on Friday he argued that he is on a broader push to root out corrupt behavior by Americans with business dealings in foreign countries, regardless of whether it involves his political rivals.

“As President I have an obligation to end CORRUPTION, even if that means requesting the help of a foreign country or countries,” Trump tweeted. “It is done all the time. This has NOTHING to do with politics or a political campaign against the Bidens. This does have to do with their corruption!”

Trump has made little previous mention of combating corruption outside the U.S. during his presidency, with the overwhelming majority of his public comments on corruption related to his accusations against Justice Department officials involved in the Russia election meddling investigation, and Democrats probing the same issues.