Sen. Ron Johnson Ronald (Ron) Harold JohnsonThe Hill's Morning Report - Sponsored by Facebook - Trump previews SCOTUS nominee as 'totally brilliant' The Hill's 12:30 Report: Ginsburg lies in repose CHC leaders urge Senate to oppose Chad Wolf nomination MORE (R-Wis.), a top ally of President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE in the Senate, spoke with a Ukrainian official about unsubstantiated claims of Ukrainian interference in the 2016 presidential election just days before Trump told the Ukrainian President he thought he should investigate former Vice President and top tier 2020 Democratic hopeful Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE.

Former Ukrainian diplomat Andrii Teilzhenko told The Washington Post on Monday that in July at the Capitol Johnson discussed unproven claims that Ukraine worked with the Democratic National Committee in 2016 to dig up dirt on onetime Trump campaign chairman Paul Manafort Paul John ManafortFBI official who worked with Mueller raised doubts about Russia investigation Our Constitution is under attack by Attorney General William Barr Bannon trial date set in alleged border wall scam MORE.

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"I was in Washington, and Sen. Johnson found out I was in D.C., and staff called me and wanted to do a meeting with me. So I reached out back and said, ‘Sure, I’ll come down the Hill and talk to you,’ ” the former diplomat told the Post.

The conversation comes amid questions over whether U.S. military aid to Ukraine was held up over the president's requests for Ukraine to open criminal investigations into Biden and allegations of interference in the 2016 U.S. presidential election.

Johnson previously told The Wall Street Journal in an interview that he was made aware by Gordon Sondland, the U.S. ambassador to the European Union (EU), of an agreement in which Ukraine would appoint a prosecutor to “get to the bottom of what happened in 2016" in exchange for the U.S. releasing military spending, a plan Johnson said at the time he opposed.

“At that suggestion, I winced,” the senator told the Journal earlier this month. “My reaction was: Oh, God. I don’t want to see those two things combined.”

The Trump administration's conversations with Ukraine have become the center of an impeachment inquiry led by House Democrats against the president, with the July 25 phone call between Trump and Ukraine's president chief among lawmakers' concerns.

Johnson's reported involvement with those conversations opens a new avenue for lawmakers who could seek answers from Johnson as to when he knew that military aid could be tied to the prospect of Ukraine's government opening one or more investigations against Democrats.

Johnson's office did not immediately return a request for comment from The Hill on Monday.