Washington — The head of the Senate Homeland Security Committee postponed a vote to subpoena a witness tied to the panel's investigation of Burisma Holdings, the Ukrainian energy firm that employed Hunter Biden, son of former Vice President Joe Biden.

Chairman Ron Johnson of Wisconsin informed committee members of the decision to delay the vote to subpoena Andrii Telizhenko, a former Ukrainian diplomat, in a message earlier Wednesday, before the committee gathered for a business meeting. Instead, the Wisconsin Republican indicated it would subpoena Blue Star Strategies, a U.S.-based government affairs firm where Telizhenko was a consultant, for records and testimony.

"Out of an abundance of caution, and to allow time for you to receive additional briefings, I will postpone a vote to subpoena records and an appearance from former Blue Star Strategies consultant Andrii Telizhenko about his work for the lobbying firm," Johnson said. "While we work through those questions, at the suggestion of both Republican and Democrat Committee members, we will instead go straight to the source and compel the same records and an appearance directly from Blue Star Strategies."

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Johnson said that over the last few weeks, senators have had a "number of bipartisan meetings and briefings to discuss our committee's ongoing investigation" and thanked members for their "engagement on this issue."

The chairman sent a letter to Homeland Security Committee members on March 1 informing them of his intent to schedule a meeting to consider the subpoena for Telizhenko, who has played a major role in spreading an unfounded theory that Ukraine interfered in the 2016 presidential election.

Republicans are seeking documents related to Telizhenko's work for Blue Star, which was a "U.S. representative" of Burisma.

In his letter, Johnson wrote that in the course of the committee's investigation into the Bidens and Ukraine, it received records from the federal government "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."

The records, however, have not been made public.

Michigan Senator Gary Peters, the committee's top Democrat, disapproved of issuing the subpoena due to concerns of Russian disinformation and instead suggested members should receive briefings regarding Telizhenko from the intelligence community and law enforcement.

The vote on the subpoena to Telizhenko was expected to be along party lines after Utah Senator Mitt Romney, a Republican, decided to vote in favor of it last week.

Johnson, along with Senate Finance Committee Chairman Chuck Grassley and Judiciary Chairman Lindsey Graham, have been probing ties between Democrats and Ukraine, including accusations of conflicts of interest between Burisma and the Bidens, for the past few months.

The three requested documents and interviews regarding Telizhenko and Alexandra Chalupa, a Ukrainian-American Democratic operative, and information from five former Obama administration officials in early December.

As Republicans charge ahead with their investigations into the Bidens, Democratic Senator Chris Murphy of Connecticut requested the inspectors general of three federal agencies and the National Archives investigate how they have responded to congressional requests for information during Democrats' impeachment inquiry compared to requests about Hunter Biden and Burisma.

Murphy said he is concerned "President Trump may be weaponizing the executive branch in advance of the 2020 elections by directing agencies to comply with congressional investigations designed to hurt his political opponents." Joe Biden has surged in the race for the Democratic presidential nomination and currently leads Senator Bernie Sanders in the national delegate race.