Trump's request for an investigation into the Bidens, directed to Ukrainian President Volodymyr Zelensky in a July 25 phone call, has prompted an increasingly escalating impeachment inquiry initiated by House Democrats.
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.
Democrats are demanding White House compliance with the subpoena by Friday, Oct. 18, and said any refusal to turn over documents will inform their impeachment efforts.
They have asked Vice President Mike Pence for Ukraine-related documents as well.
The impeachment investigation into President Donald Trump widened on October 4 into a constitutional battle between the executive branch and Congress, as Democrats subpoenaed White House officials and the president signaled his administration would not cooperate.
"The White House has refused to engage with-or even respond to-multiple requests for documents from our Committees on a voluntary basis", the chairmen wrote.
Panel Chairman Rep. Elijah Cummings had threatened the subpoena Wednesday, after the White House ignored two letters in September seeking the documents.
The New York Times said the unnamed official had "more direct information" about the events surrounding Mr Trump's phone call with Mr Zelensky.
Speaking to reporters in Greece, Pompeo dismissed questions about Trump's attempts to push Ukraine and China to investigate a Democratic political rival.
It is that last message that Donald Trump and Republicans have seized upon as proof that the president did not offer anything in return for an investigation into the Bidens.
"What we're talking about here is not about personality, it's not about policy differences - that's to be taken up in the election", Pelosi said.
He also addressed a notion Mr Trump has long held that Ukraine interfered in the 2016 U.S. presidential election, a theory that runs counter to the United States intelligence community's findings that it was Russian Federation that meddled in the campaign.
The second official is among those interviewed by the intelligence community inspector-general to corroborate the allegations of the original whistle-blower, one of the people said.
Trump acknowledges that Democrats "appreciate the votes" to proceed, however predicts they'll "pay a fine worth at the polls".
Democrats accused Trump of speeding down "a path of defiance, obstruction and cover-up".
At the time, the Trump administration was withholding hundreds of millions in aid for Ukraine and Democrats said they suspect Trump was using USA foreign policy and taxpayer money for his personal political gain.
However, there is no credible evidence available that Biden was involved in such schemes.
Fox News host Chris Wallace has warned that testimony from former US special representative to Ukraine Kurt Volker is highly damaging to President Donald Trump and his attorney Rudy Giuliani.
Late Thursday, House investigators released a cache of text messages that showed top USA diplomats encouraging Zelenskiy to conduct an investigation linked to Biden's family in return for granting a high-profile visit with Trump in Washington.
Asked by The Associated Press about Trump's comment Thursday that the USA has an "absolute right" to ask foreign leaders to investigate corruption cases, Zelenskiy said that Ukraine is "open" and that all the cases under investigation are "transparent".
The development came as Trump said the White House was also preparing a letter - this one to House speaker Nancy Pelosi.