"I did read the transcript. It remains troubling in the extreme. It's deeply troubling," Romney told reporters. "Clearly what we've seen from the transcript itself is deeply troubling."

Romney's comments came after the White House released a five-page partial transcript of a call that has sparked a days-long political storm for the administration.

“There's a lot of talk about Biden's son, that Biden stopped the prosecution and a lot of people want to find out about that so whatever you can do with the Attorney General would be great," Trump told Zelensky in the July 25 call.

The call, and a whistleblower complaint reportedly tied to Trump, lead House Democrats to formally begin an impeachment inquiry against Trump on Tuesday.

Republicans have hounded Pelosi over the decision. But Romney on Wednesday declined to directly criticize the speaker.

“That's not advice I'm going to be providing to the House or to the Speaker. She's able to do what she feels is right. That’s up to her. At this stage the process is to continue to gather information but clearly what we’ve seen from the transcript itself is deeply troubling," he said.

.@jmartNYT: appropriate for the House to begin this inquiry on impeachment?



ROMNEY: "That’s not advice I’m going to be providing to the House Speaker, she is able to do what she believes is right...clearly what we’ve seen from the transcript itself is deeply troubling." pic.twitter.com/8mw11r1jRj — Alan He (@alanhe) September 25, 2019

Most Senate Republicans have been wary of getting too far from Trump amid the fight, or argued they need more information about the whistleblower complaint. The Senate Intelligence Committee is expected to get briefed by the intelligence community inspector general on Thursday.

But Romney became one of the first GOP senators to raise concerns about the phone call.

"If the President asked or pressured Ukraine’s president to investigate his political rival, either directly or through his personal attorney, it would be troubling in the extreme. Critical for the facts to come out," he tweeted over the weekend

Trump tweeted a video on Monday mocking Romney over his failed 2012 presidential bid, comparing it with Trump's own success four years later.

Romney brushed off the tweet when asked about it on Tuesday.

“I’d forgotten I’d lost, so I appreciate the reminder," he joked to reporters.

Romney added: "There's a process the House is pursuing. The Senate is also looking at the testimony of the whistleblower."