The latest on the Trump impeachment inquiry

US Ambassador to the European Union Gordon Sondland is scheduled to testify before three House committees on Tuesday, two congressional sources tell CNN. 

Sondland is expected to attend, one of the sources said.

He had originally been scheduled for later next week.

What we know about Sondland: The ambassador is mentioned in a series of text messages between US diplomats and a Ukrainian aide. The messages, which were released last night, show how a potential Ukrainian investigation into the 2016 election was linked to a desired meeting between Ukrainian President Volodymyr Zelensky and President Trump.

In one exchange, Sondland seemed to downplay the concerns raised by his counterpart in Kiev.

"Gordon, one thing Kurt and I talked about yesterday was Sasha Danyliuk's point that President Zelenskyy is sensitive about Ukraine being taken seriously, not merely as an instrument in Washington domestic, reelection politics," Ambassador William "Bill" Taylor, the charge d'affaires at the US Embassy in Kiev, wrote on July 21.

Sondland replied, "Absolutely, but we need to get the conversation started and the relationship built, irrespective of the pretext."

On September 1, Taylor raised a question about the conditions upon which the aid was stalled and a White House visit by Zelensky would be predicated.

"Are we now saying that security assistance and WH meeting conditioned on investigations?" Taylor asked.

"Call me," Sondland replied.

Sondland has been the ambassador to the European Union since late June 2018.

CNN Political Director David Chalian analyzes a series of text messages between US diplomats and a senior Ukrainian aide in the first episode of "The Daily DC: Impeachment Watch" podcast.

The text messages, which were released last night, show how a potential Ukrainian investigation into the 2016 election was linked to a desired meeting between Ukrainian President Volodymyr Zelensky and Trump.

Chalian is joined by CNN National Correspondent Athena Jones and New York Times White House Correspondent and CNN Political Analyst Maggie Haberman.

Listen to the podcast here.

Democratic presidential candidate Joe Biden reacted to President Trump’s recent comments regarding him and his son Hunter’s alleged overseas dealings.

Some context: Trump has repeatedly claimed that Hunter Biden has engaged in nefarious behavior overseas.

"Biden is corrupt, his son is corrupt," Trump said today. "His son takes out billions of dollars, billions, and he has no experience."

Trump has repeatedly accused both Bidens of corruption involving China and Ukraine. There is no evidence of wrongdoing by the Bidens.

A spokesperson for Arizona State University tells CNN this afternoon that Kurt Volker is still the executive director of the McCain Institute and that there is nothing to announce. 

Volker met with staff of the institute this afternoon and two sources familiar with the meeting tell CNN that Volker did not resign in a staff meeting and said he has no imminent plans to resign.

CNN reported earlier today that Volker was planning to resign, according to a source familiar with the matter. 

One of the sources who was in the room for the staff meeting at the McCain Institute said that Volker told staff he had seen the reports about his resignation, but the source said Volker said that they were premature or presumptuous and that he had had no immediate plans to resign. Volker wanted to keep doing the job, but recognized that there were conversations going on with people he reports to and that he might have to step away from the role. Volker said it was whatever is best for the McCain Institute, the source said.

The source said that Volker had opened up the meeting with a short summary of what he’d been up to the past few days. The source said there was a general feeling that the staff wanted him to stay, and staff didn’t express concerns during the meeting about the events of the past two weeks affecting the institute’s work.

About Volker: He was the first witness to appear before three congressional committees and to be deposed on the whistleblower complaint, which alleges that President Trump tried to pressure Ukraine to investigate his Democratic rival Joe Biden.

The White House letter regarding House Democrats' request for information related to the impeachment inquiry may come Monday, a source familiar said.

The source said there’s some internal debate over whether to release it now.

Some background: Earlier this week, Democrats told the White House to expect subpoenas related to the Ukraine matter. 

House Speaker Nancy Pelosi has not yet held a full vote in the House approving of the impeachment inquiry. Trump’s allies have argued that means the process has not formally begun. 

Pelosi said in a letter Thursday to House GOP leader Kevin McCarthy there "is no requirement under the Constitution, under House Rules, or House precedent that the whole House vote before proceeding with an impeachment inquiry.”

Vice President Mike Pence's office criticized a letter it received today calling for documents relating to the ongoing impeachment inquiry.

His press secretary Katie Waldman said the letter "does not appear to be a serious request but just another attempt by the do nothing Democrats to call attention to their partisan impeachment."

Read Waldman's full statement below:

Some background: When President Trump was asked if the White House would comply with subpoenas for information related to the impeachment inquiry, he said "that's up to the lawyers." Democrats have have warned the White House and Trump administration against interfering with the probe.

President Trump will be speak at Turning Point USA's Young Black Leadership Summit this afternoon at 4:30 p.m. ET, according to the White House schedule.

It's unclear if President Trump will address the impeachment inquiry during his remarks.

According to the summit's website, attendees of the three-day event "will hear from some of the nation’s most well-known conservative leaders and activists, receive first-class professional development and leadership training, and network with other attendees and organizations from all across the country."

Turning Point USA is a conservative advocacy group.

The chairmen of the House Intelligence, Oversight and Foreign Affairs committees have written to Vice President Mike Pence asking that he turn over Ukraine-related documents by Oct. 15.

The chairmen said in the letter that the recent reports about Pence include: “Specific references to a member of your staff who may have participated directly in the July 25, 2019, call, documents you may have obtained or reviewed, including the record of the call, and your September 1, 2019, meeting with the Ukrainian president in Warsaw, during which you reportedly discussed the administration’s hold on US security assistance to Ukraine.”

What is this about: CNN reported this week that Pence was told about the July 25 call between President Trump and Ukrainian President Volodymyr Zelensky the day after the call happened.

However, the sources would not say whether in that conversation Pence was told what Trump said about former Vice President Joe Biden and his son. A third source said the vice president was not briefed on Biden, but did say information about the call was made available to him.

The three sources familiar confirm Pence was provided a transcript of Trump's call with Zelensky in his briefing book the day after the call.

News regarding President Trump and the Ukraine controversy continues to trickle out, with the President claiming his efforts are intended to end corruption, "even if that means requesting the help of a foreign country."

If you're just tuning in, here are the key developments:

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