A U.S. District court judge has put a former British spy one step closer to facing questions under oath about the controversial dossier he authored alleging President Donald Trump‘s 2016 campaign team plotted with Russian agents.

A ruling by Judge Ursula Ungaro allows lawyers for a Russian technology executive named in the dossier to seek British approval to question onetime MI6 agent Christopher Steele about the funding and sourcing of the dossier under oath. The request was made as part of a libel suit brought by Webzilla CEO Aleksej Gubarev against the website Buzzfeed, which was first to publish the dossier Steele prepared.

“I suspect that I’ll be the first to speak to him,” Gubarev’s attorney, Valentin Gurvits, told ABC News this week. “I know that he is trying very hard to prevent that from happening.”

The potential interview with Steele is part of a widening effort to pierce the secrecy surrounding the now infamous dossier that raised the first questions about then-candidate Trump’s ties to Russia. The 35-page document contains a range of unverified allegations – some of which have been discredited – laying out a history of ties between several Trump associates and Russia operatives. It also levels salacious claims about Trump’s own behavior during a visit to Moscow in 2013 – claims Trump later refuted and denounced during a Jan. 11 news conference.

“I think it was disgraceful, disgraceful that the intelligence agencies allowed any information that turned out to be so false and fake out,” Trump said.

Interest in the funding and sourcing for the dossier led the Senate Judiciary Committee to summon Glenn Simpson, the head of the Washington, D.C.-based research firm Fusion GPS that commissioned Steele’s work, to a closed session meeting scheduled for Tuesday. In a letter to Simpson, Senate Judiciary Chairman Chuck Grassley, R-Iowa, indicated he wants Simpson to reveal who first hired him to investigate Trump’s Russia ties and which government agencies received copies when it was completed.

“We are interested in the history of the dossier, including how it was funded, compiled and how it was used,” a Grassley aide told ABC News.

“There’s certainly plenty of evidence that Russia worked to interfere with our democratic process … but allegations that the Trump campaign was involved stem largely from the contents of a salacious and unverified anti-Trump dossier, whose creation was overseen by Fusion GPS for political purposes,” another Republican Judiciary Committee aide said. “Reports that the FBI then used the dossier as a roadmap for its investigation, attempted to hire the former British spy who was compiling it, and may have relied on it to obtain special surveillance authority raises significant oversight and civil liberties concerns that warrant scrutiny.”

A source familiar with the Fusion GPS negotiations with the Senate Judiciary Committee told ABC News that Simpson is ready and willing to answer questions.

“Mr. Simpson will participate in a transcribed interview with the committee, and so far is the only person who has been willing to do so,” the source said.

Both Simpson and Steele have also been drawn into defamation lawsuits filed by the Russian tech mogul, Gubarev, in Great Britain and in the U.S. District Court in the Southern District of Florida.

Gubarev’s named appeared in the dossier, which was later published online by Buzzfeed. The dossier alleges that Gubarev had been recruited under duress by Russian agents, and that his company had transmitted viruses, planted bugs, stolen data and conducted “altering operations against the Democratic Party leadership” during the 2016 elections. Gubarev has strongly denied all of those claims.

“His response is it is a lie. It is a fabrication,” Gurvits, Gubarev’s attorney, told ABC News. “Never happened.”

Buzzfeed initially published the dossier with references to Gubarev but later redacted Gubarev’s name and the name of his company on the copy of the document published by the website. Attorneys for Buzzfeed, Steele and Simpson declined to comment.

Gubarev’s lawsuit has attracted attention because his lawyers have expressly stated they want to ask Steele – a former British intelligence officer stationed in Moscow – to identify the sources he relied upon to prepare the dossier.

A Russian who lives in Cyprus, Gubarev and his company operates one of the largest web-hosting networks in Europe. In a lengthy interview with ABC News, his lawyer rejected the suggestion that Gubarev is acting as a surrogate for the Kremlin who is attempting to use the U.S. courts to unmask the identities of Steele’s Russian sources.

“It’s clear that we’re not acting on behalf of the Russians,” Gurvits told ABC news. “We are acting on behalf of a businessman who has less ties, frankly, with Russia than he does with the United States. Forty percent of his business comes from the United States. This is not a relationship that a sane person would ever mess with.”

If he has the opportunity to take Steele’s sworn testimony, Gurvits said, “my number-one question is, ‘Why was this allegation about my clients included [in the dossier]?” he said. “Where did you get it? What did you do to verify it? And who did you communicate it to?”

In June court filings in the United Kingdom, Steele’s attorneys answered the last question, telling the court he shared his findings with a representative of Sen. John McCain. Arrangements were then made through an intermediary to get the document to McCain, who chairs the Senate Armed Services Committee, “so that it was known to … the United States governments at a high level by persons with responsibility for national security,” Steele’s filing in British court says.

McCain released a statement in January saying he then “delivered the information to the director of the FBI,” because he had been unable to assess the accuracy of the claims on his own. “That has been the extent of my contact with the FBI or any other government agency regarding this issue.”

As for who funded Steele’s research effort in the first place, that remains a mystery. British court records have only identified the clients as a Republican opponent of Trump’s initially, and a Democratic funder later. Grassley aides told ABC News that Judiciary Committee investigators plan to ask Simpson Tuesday to reveal the identity of his clients, but they are not optimistic they will get an answer.

Attorneys for Fusion have already indicated to the committee that its client relationships are confidential.