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. (Kelly Presnell/Arizona Daily Star via AP)

WASHINGTON - The Latest on President Donald Trump and the Democrats' impeachment inquiry (all times local):

6:25 p.m.

A House committee has sent a subpoena to the White House demanding documents that could provide details on President Donald Trump's effort to push Ukraine to produce information that could damage Joe Biden's presidential run.

The subpoena was issued by the House Oversight and Reform Committee as part of Democrats' impeachment investigation of Trump.

Trump has resisted Democratic attempts to produce documents and administration witnesses for the impeachment inquiry.

The subpoena seems likely to escalate the clash between the two branches of government.

Panel Chairman Rep. Elijah Cummings had threatened the subpoena Wednesday, after the White House ignored two letters in September seeking the documents.

Trump was withholding military aid to Ukraine when he used a July phone call to ask its president to investigate Biden for corruption, an unfounded allegation

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3:45 p.m.

House investigators want Vice-President Mike Pence to give them documents that could shed light on whether he helped President Donald Trump pressure Ukraine to investigate Joe Biden.

In a letter to Pence on Friday, the Democratic chairmen of three House committees cite reports that a Pence aide may have listened to the July phone call in which Trump pushed Ukraine's president to investigate unfounded charges that Biden was involved in corrupt activities there.

They say they also want to learn more about Pence's Sept. 1 meeting with President Volodymyr Zelenskiy.

The letter says there are "questions about any role you may have played in conveying or reinforcing the President's stark message to the Ukrainian President."

Former Vice-President Joe Biden is seeking the Democratic presidential nomination.

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11:35 a.m.

President Donald Trump is insisting that his call for China to investigate former Vice-President Joe Biden will have no bearing on upcoming high-stakes trade talks with the nation.

Trump is telling reporters at the White House Friday that, "one thing has absolutely nothing to do with the other."

Negotiations between the U.S. and China are set to resume next week as a protracted trade war continues.

Trump on Thursday publicly encouraged China to investigate Biden and his son, Hunter, snubbing his nose at an impeachment inquiry into whether a similar, private appeal to Ukraine violated his oath of office.

Trump says he believes China wants to make a deal.

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11:20 a.m.

President Donald Trump is denying there was quid pro quo as he sought for the Ukrainian government to investigate Joe Biden, and says he didn't do it for political purposes.

Trump says: "We are looking at corruption, we're not looking at politics."

He adds: "I believe there was tremendous corruption with Biden."

Trump has asked Ukraine and China to launch probes into the former vice-president and 2020 Democratic hopeful, alleging without evidence that there was misconduct by Biden and his son, Hunter.

He claims his call for the investigations wasn't political, because "I never thought Biden was going to win" the primary.

Trump says of rooting out corruption: "I actually feel I have an obligation to do that."

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11:10 a.m.

President Donald Trump is acknowledging that Democrats in the House have the votes to begin a formal impeachment inquiry into his conduct.

Trump is telling reporters at the White House that while, "Republicans have been very unified," the "Democrats, unfortunately, they have the votes."

But he's insisting the move will backfire on the party, saying: "I really believe that they're going to pay a tremendous price at the polls."

Trump said Friday the White House would be sending a letter to House Speaker Nancy Pelosi to formally object to the inquiry. It's expected to say officials won't co-operate with the probe because it was initiated without a vote of the House.

Pelosi last week announced that the House was beginning the formal inquiry but didn't seek the consent of the full chamber.

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11:05 a.m.

White House economic adviser Larry Kudlow says he "seriously" doubts China's response to President Donald Trump's call for the rival nation to investigate a Democratic political rival will play a role in upcoming high-stakes trade negotiations between the nations.

Kudlow tells reporters at the White House, "I seriously doubt that that is going to be part of the talks."

Trump on Thursday called on China to investigate former Vice-President Joe Biden and his son. Talks between the countries are set to resume next week.

Kudlow also says he's unaware of the contents of a June phone call between Trump and Chinese President Xi Jinping in which CNN reports Trump brought up the political prospects of both Biden and Sen. Elizabeth Warren.

Kudlow is calling the call and questions about the president's conduct "way out of my lane."

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12:30 a.m.

The White House is preparing to formally object to the Democrats' impeachment inquiry as soon as Friday, saying it won't co-operate with the probe because it was initiated without a vote of the House.

The White House Counsel's Office was preparing to send a letter to House Speaker Nancy Pelosi objecting to the form of the impeachment investigation, a person familiar with the matter said late Thursday, speaking on condition of anonymity to discuss the letter before its dissemination.

Pelosi last week announced that the House was beginning the formal inquiry but didn't seek the consent of the full chamber, as was done for impeachment investigations into former Presidents Richard Nixon and Bill Clinton.

Rudy Giuliani, the president's personal attorney, confirmed that the letter was forthcoming.

News from © The Associated Press, 2019