Rep. Doug Collins (R-Ga), right, and House Judiciary Chairman Rep. Jerrold Nadler (D-N.Y.), left, during a meeting earlier this month. (Mark Wilson/Getty Images)

The top-ranking Republican on the House Judiciary Committee is urging that special counsel Robert S. Mueller III be called to testify before the panel this month.

Rep. Douglas A. Collins (R-Ga.) in a letter Monday to House Judiciary Chairman Jerrold Nadler (D-N.Y.) said that he would like to see Mueller testify during the week of April 22, calling it “undoubtedly the best way” for the American people to learn about “the full contours” of the investigation into Russian election interference in 2016.

Last week, the Democrat-led committee voted to authorize Nadler to subpoena the full report and underlying documents produced by Mueller during his investigation into whether the Trump campaign and Russia coordinated during the presidential election and whether Trump sought to obstruct the probe.

According to a four-page summary of top-line findings of Mueller’s report provided to Congress by Attorney General William P. Barr, Trump and his campaign did not illegally coordinate with Russia, but Mueller left open the question of whether Trump obstructed justice. Barr said he concluded that Trump did not commit obstruction.

Nadler went on Twitter later Monday to say he agrees that Mueller should appear before the committee but that the committee needs to see the full report and hear from Barr first in order “to ask Special Counsel Mueller the right questions.”

“We look forward to hearing from Mr. Mueller at the appropriate time,” Nadler said.

Democrats are increasingly questioning whether Barr, a Trump appointee, was a neutral arbiter on what transpired.

Collins, who has objected to a committee request to Barr that includes grand jury materials, urged a different course in his letter.

“For nearly two years, Special Counsel Mueller oversaw an investigation that issued more than 2,800 subpoenas, executed nearly 500 search warrants, and interviewed approximately 500 witnesses,” he wrote. “Attorney General Barr was never a part of this investigation, and instead simply reviewed the Special Counsel’s final report and has provided Congress, so far, with the Special Counsel’s principal conclusions. While he can testify surrounding his decision to provide the committee with principal conclusions, it is Special Counsel Mueller who is best-positioned to testify regarding the underlying facts and material in which you are so interested.”