Washington (CNN) Republican Sen. Mitt Romney said Monday that he has had discussions with his GOP colleagues and it is "increasingly likely" that others would join his ongoing push for former national security adviser John Bolton to testify in the impeachment trial of President Donald Trump.

"I've said for some time that I would hope to hear from John Bolton. I think with the story that came out yesterday that it is increasingly apparent that it would be important to hear from John Bolton," the Utah Republican said. "I think it's increasingly likely that other Republicans will join those of us who think we should hear from John Bolton."

Romney, who has before expressed frustration with Trump, previously indicated that he would be interested in hearing testimony from Bolton. "I think it's very likely I'll be in favor of witnesses, but I haven't made a decision finally yet and I won't until the testimony is completed," he said.

"I am not going to speak for any other Republican senators," Romney said when asked Monday who he has spoken with. "I have spoken with others who have opined on this as well."

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