Senate Homeland Security and Governmental Affairs Committee Chairman Ron Johnson (R-Wis.) is planning to force a vote on the first subpoena related to his probe involving Ukrainian energy firm Burisma Holdings and former Vice President Joe Biden’s son Hunter Biden.

Johnson sent a letter to members of his committee on Sunday saying that it is his “intention to schedule a business meeting to consider a committee subpoena” of a former consultant for Blue Star Strategies, which Johnson noted worked as a U.S. representative for Burisma.

“As part of the committee’s ongoing investigation, it has received U.S. government records indicating that Blue Star sought to leverage Hunter Biden’s role as a board member of Burisma to gain access to, and potentially influence matters at, the State Department,” Johnson wrote in the letter to committee members.

Sen. Gary Peters (Mich.), the top Democrat on the committee, has notified Johnson that he objects to issuing the subpoena over concerns that it could bolster Russian disinformation efforts. Without Peters’s support, Johnson will need a simple majority of the GOP-controlled panel to vote to issue the subpoena.

Peters, in a statement, noted that Russia is trying to interfere in the 2020 election, and urged Congress from avoiding inadvertently helping that effort.

“We need to take every step to ensure the credibility and resources of the U.S. Senate are not used to advance interference efforts by foreign adversaries that seek to undermine our democracy or put our national security at risk,” he said.

If Johnson is successful, it would mark the first subpoena to come out of the months-long Republican investigation into Burisma and Hunter Biden, who previously served on the Ukrainian company’s board. It would also escalate what has been a probe that, so far, has largely been limited to letters and some document production.

Johnson wants to subpoena Andrii Telizhenko, a former consultant for Blue Star. Telizhenko, according to Johnson, has said he wants to “cooperate fully” with the investigation but is limited by a nondisclosure agreement.

“Because Mr. Telizhenko’s records and information would be responsive to the committee’s requests, and Blue Star has refused to provide them, a subpoena to Mr. Telizhenko for these records is appropriate at this time,” Johnson wrote in the letter.

“Accordingly, I will be scheduling a vote in the near future to approve issuing the enclosed subpoena,” Johnson continued.

Johnson defended his decision in the four-page letter to committee members, arguing it was “narrowly drafted” to only request documents related to Burisma Holdings and Blue Star Strategies, and for Telizhenko to meet with committee staff to discuss the issue.

“Blocking the receipt of relevant records, as any committee member voting against this subpoena would be doing, only heightens the risk of ‘disinformation’ because Congress would not have access to all pertinent information,” Johnson added.

The letter to all committee members comes after Johnson sent a letter to Peters late last month informing him that he wanted to issue the subpoena. 

The timing of Johnson’s letter immediately raised eyebrows because it came one day after Biden won the South Carolina Democratic primary, adding a new boost of momentum into his 2020 campaign. Johnson has denied that he is targeting the Bidens because of Joe Biden’s presidential campaign.

Republicans have homed in on Hunter Biden’s position on the board of Burisma, including seeking to tie then-Vice President Joe Biden’s push in 2016 for the dismissal of Ukrainian Prosecutor General Viktor Shokin to Hunter Biden’s business interests. They’ve also argued that allowing Joe Biden to work on Ukraine policy while his son was on the board of Burisma was a conflict of interest.

The former vice president has denied wrongdoing. There’s no evidence that either Biden engaged in any criminal wrongdoing, and fact checkers have debunked claims that he was working with his sons interest in mind.

But that’s done little to tamp down questions from Republicans, particularly on whether or not there was a conflict of interest. Hunter Biden’s position on the board of Burisma was at the center of President Trump’s impeachment trial in the Senate, where Trump was acquitted last month of the two House-passed articles of impeachment.

Tensions have flared more recently after a top Senate Democrat disclosed that the Treasury Department had handed over documents pertaining to Johnson and Sen. Chuck Grassley’s (R-Iowa) wide-ranging investigation, which includes Hunter Biden and Burisma.

Republicans blasted the disclosure as a “leak” meant to undermine their investigation.

A spokeswoman for Sen. Ron Wyden (D-Ore.), the top Democrat on the Finance Committee, did not disclose what was in the documents handed over by the Treasury Department.

A spokesman for Grassley said last week that they have also received State Department documents.

—This report was updated at 7:37 p.m.