Washington (CNN) Senate Majority Leader Mitch McConnell said Tuesday "we're going to find out what happened" about a whistleblower's complaint regarding President Donald Trump and said he expects the Senate Intelligence Committee will conduct a "responsible, rather apolitical, at least bipartisan" probe of the matter.

But the Kentucky Republican and his fellow GOP senators did not explicitly commit to pushing for the full complaint turned over to the committee.

McConnell's pledge came the same day Trump announced he would release an "unredacted transcript" of the call Trump made to Ukrainian President Volodymyr Zelensky during which Trump encouraged the Ukrainians to investigate former Vice President Joe Biden and his son Hunter Biden.

It also came on the same day House Speaker Nancy Pelosi announced a formal impeachment inquiry to investigate the allegations.

On Monday McConnell blasted Democrats for what he said was a politicization of the issue before the facts were known.

The Senate Intelligence Committee plans to meet in a classified setting Thursday with the Acting Director of National Intelligence Joseph Maguire and the Inspector General for the Intelligence Community Michael Atkinson where they will be asked to testify about what they know about the whistleblower complaint.

McConnell said the Intelligence Committee, which is chaired by Sen. Richard Burr, a Republican of North Carolina, would look into the issue.

"We're going to find out what happened. In the Senate, through a process pre-established through the Intelligence Committee behind closed doors initially with the acting director of DNI," McConnell said. "I think that is the responsible, rather apolitical, at least bipartisan way to proceed with what we think we know at this particular point."

Burr was tight-lipped Monday about how his committee would respond to the complaint, although finally said he want to "bring the interested parties in" before the committee.

The top Democrat on the committee is Sen. Mark Warner of Virginia.

"This is one step in a process. This is an orderly process, where the Committee, the full Committee, will get a chance to hear from both the IC Inspector General, Mr. (Michael) Atkinson , and the Acting DNI, Admiral Maguire," Warner said. "But again, we're going to take this one step at a time, and I think it's terribly important to get the facts."

A Senate Democrat source told CNN that Democrats are trying to remain focused on obtaining the whistleblower complaint itself despite Trump's announcement Tuesday he will release the transcript from his call with Zelensky. The thinking is, per this source, that the concerns about Trump's conduct do not hinge completely on what is in the transcript.

Multiple sources have also noted that the Democrats maintain the acting DNI is required to provide the complaint to Congress by law.

The second-ranking Republican, Sen. John Thune, did not say if Republicans will insist the administration turn over the whistleblower's formal complaint.

"We'll know a lot more when the Intel Committee meets with them this week," Thune said. "If it's an intelligence related issue then it probably falls under the committee's jurisdiction and I'm sure they will be anxious to get all those answers."

Also Tuesday, the Senate adopted by unanimous consent a resolution authored by Minority Leader Chuck Schumer urging the administration to provide the full compliant to Congress.

Schumer, D-New York, said the resolution was "aimed at a recalcitrant executive branch, which has blocked the ability for the committees to see the complaint, even though the law requires it."

McConnell said Republicans would go along with the resolution in the spirit that it would assist the Intelligence Committee conduct its investigation.