- House Intelligence Committee Chairman Adam Schiff said the exact timing of the testimony depends on when the director of national intelligence completes the security clearance process for the whistleblower's lawyers.
- He said the inquiry will focus on "the fundamental breach of the president's oath of office."
- President Trump, in a flurry of posts on Twitter over the weekend, slammed the impeachment inquiry as a "scam" and a "witch hunt" and called on Schiff to resign.
House Intelligence Committee Chairman Adam Schiff said Sunday that an agreement has been reached for the whistleblower at the center of the impeachment inquiry into President Donald Trump to testify before Congress.
In an interview on the ABC program "This Week," Schiff, D-Calif., said he expects the whistleblower to testify "very soon," but timing depends on when the director of national intelligence completes the security clearance process for the individual's lawyers.
"We'll get the unfiltered testimony of that whistleblower," Schiff said.
The whistleblower's lawyer, Mark Zaid, said Sunday that they are working with both parties in the House and the Senate, but no date or time has been set yet for testimony. Protecting the whistleblower's identity is paramount, Zaid said.
The whistleblower filed a complaint expressing concern that Trump was "using the power of his office to solicit interference from a foreign country in the 2020 U.S. election."
The redacted complaint, released by the House Intelligence Committee on Thursday, details a July 25 call in which Trump asked Ukraine's president to "do us a favor" and investigate Democratic presidential candidate Joe Biden and his son Hunter for corruption.
It's illegal under campaign finance law to solicit help from foreign nationals, foreign governments, foreign businesses or foreign political parties.
Trump froze nearly $400 million in military aid to Ukraine before the July 25 call, raising concerns that he was seeking a quid pro quo with Kyiv, an allegation that the president and his supporters deny.
Trump said he halted the aid, which was later released, because European nations were not contributing enough to Ukraine, which is fighting a war with Russian-backed separatists in its eastern region. The European Union and European financial institutions have contributed more than $16 billion in assistance to Ukraine since 2014, according to The Associated Press.
House Speaker Nancy Pelosi announced an official impeachment inquiry into Trump on Tuesday in response to the revelations about Trump's call with Ukraine's president, accusing Trump of betraying his oath of office. The nature of the call was reported by the media before the complaint was publicly released.
Schiff said Sunday that the inquiry will focus on "the fundamental breach of the president's oath of office." His committee, one of six conducting investigations, is taking the lead in the probe.
The whistleblower, a CIA employee who was posted to the White House, said in the complaint that administration officials were "deeply disturbed" by Trump's call and intervened to "lock down" records of the conversation by moving them to a server normally used to store classified information.
The White House has reportedly also sought to limit access to Trump's phone calls with Russian President Vladimir Putin and Saudi Crown Prince Mohammed bin Salman. Schiff said his committee would seek access to records for those conversations as well if they were stored on the same classified server as the records of the Ukraine call.
"If those conversations with Putin or with other world leaders are sequestered in that same electronic file that is meant for covert action, not meant for this, if there's an effort to hide those and cover those up -- yes, we're determined to find out," Schiff said.
Trump, in a flurry of posts on Twitter over the weekend, slammed the impeachment inquiry as a "scam" and a "witch hunt" and called on Schiff to resign from Congress. In a video message Saturday, the president told his supporters that Democrats were trying remove him from office to take away their guns and their health care.
"It's all very simple -- they're trying to stop me, because I'm fighting for you," Trump said.
Sen. Lindsey Graham, a close confidant of Trump, dismissed the whistleblower's complaint as hearsay.
"Every American deserves to confront their accuser, so this is a sham as far as I'm concerned," Graham, R-S.C., told the CBS program "Face the Nation" on Sunday. "We're not going to try the president of the United States based on hearsay."
Public support for the impeachment inquiry, however, appears to be growing. A CBS News poll released Sunday found that 55% of Americans support the inquiry while 45% are opposed to it. Democrats are overwhelmingly in favor of it; Republicans are overwhelmingly opposed; and independents are divided about equally, the poll found.
-- CNBC's Jacob Pramuk and Dan Mangan contributed to this report