Will hold off on vote:?Nancy Pelosi on impeachment probe against Trump

US House Speaker Nancy Pelosi said on Tuesday that the House of Representatives does not plan at this time to hold a full vote to authorise an impeachment investigation into President Donald Trump, while House Intelligence Committee chairman Adam Schiff pointed to information gathered in witness testimony despite a 'complete effort by the administration to stonewall' the probe.

"There is no requirement that we have a vote and so at this time we will not be having a vote," Pelosi said at a press conference on Tuesday.

The White House has criticised the lack of such a vote and vowed not to cooperate with what it describes as an illegitimate investigation.

The investigation is focused on the July call in which Trump pressed Zelensky to have Ukraine officials investigate Biden and his businessman son, Hunter Biden, who had been on the board of a Ukrainian energy company.

Hunter Biden, 49, denied doing anything improper and Joe Biden has denied Trump's allegations of corruption.

Democrats have accused Trump of pressuring a vulnerable US ally to dig up dirt on Biden after withholding USD 391 million in US security aid intended to help combat Russian-backed separatists in the eastern part of Ukraine.

Trump has denied wrongdoing and defended his request to Zelensky during the phone call, which prompted a formal whistleblower complaint by a person with a US intelligence agency.

The Pentagon said on Tuesday that it was unable to share documents with the House of Representative committee pursuing an impeachment inquiry of President Donald Trump, citing "legal and practical concerns."

In a letter seen by Reuters, the Pentagon said the House of Representatives did not have a resolution authorising an impeachment investigation, adding that it could not produce documents in the eight days it was given to comply with the subpoena.