The special counsel Robert Mueller's office on Wednesday revealed the names of two potential witnesses it is accusing Paul Manafort, the former chairman of President Donald Trump's campaign, of trying to tamper with in the Russia investigation.

The witnesses are Alan Friedman and Eckart Sager, two former journalists who were involved in a lobbying group's efforts in 2013 to bolster the US reputation of Ukraine's president at the time, Viktor Yanukovych.

Shortly after Mueller's office filed documents in court revealing Friedman's and Sager's names, prosecutors refiled the documents with redactions.

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The special counsel Robert Mueller's office revealed on Wednesday the names of two potential witnesses it is accusing Paul Manafort, the former chairman of President Donald Trump's campaign, of trying to tamper with in the Russia investigation.

The people are Alan Friedman and Eckart Sager, two former journalists based in Europe. Friedman and Sager spearheaded efforts by the Hapsburg Group — a lobbying organization consisting of former European leaders — to lobby on behalf of Viktor Yanukovych, then Ukraine's president, in Europe and the US.

Shortly after filing documents that revealed Friedman's and Sager's names, the special counsel refiled the court documents with the names redacted.

Manafort and an associate, the former Russian intelligence operative Konstantin Kilimnik, were indicted last week on charges of obstruction of justice and conspiracy to obstruct justice based on accusations they tried to tamper with witness testimony.

In a separate filing last week, prosecutors detailed Manafort's and Kilimnik's activities that are said to have taken place over several days in February, after Manafort's longtime associate Rick Gates pleaded guilty and began cooperating with prosecutors. Friedman and Sager were initially named as "Person D1" and "Person D2" in court documents.

In one communication, Manafort sent Friedman a message with a link to a Business Insider article about the Hapsburg Group's activities. The article said, among other things, that the Hapsburg Group worked in the US and in Europe. One minute after sending the article, Manafort sent Friedman a message saying he had "made clear" that the group worked only in Europe.

Friedman subsequently contacted Mueller's office and said he believed Manafort's messages were part of an effort to "suborn perjury," or coax them into giving false testimony, because he knew the group worked in both Europe and the US.

When Friedman didn't respond to Manafort's messages, Kilimnik reached out to Sager to relay the same message and told Sager that Manafort had been attempting to reach Friedman.

In light of the accusations, prosecutors asked US District Judge Amy Berman Jackson in Washington, DC, to revoke Manafort's bail. She is set to make a decision on the matter on Friday.

Manafort's lawyers argue that the Hapsburg Group's lobbying campaign on Yanukovych's behalf was in Europe and that Manafort's and Kilimnik's outreach to Friedman and Sager proves that. Manafort's arraignment on the witness-tampering charge is also scheduled for Friday, and he is expected to plead not guilty.

In response to Manafort's lawyers' claim that the Hapsburg Group's lobbying was limited to Europe, Mueller's office submitted two memos involving Friedman, Sager, Manafort, and Yanukovych to the court in a Tuesday-night filing. The memos appear to show the group working to improve Yanukovych's image in the US in addition to Europe.

Manafort's and the Hapsburg Group's outreach to Congress

Viktor Yanukovych. REUTERS/Alexander Demianchuk

The first memo was an email from Sager to Friedman sent in March 2013, with the subject "Great First Day."

In addition to meeting with people from two companies, Sager also told Friedman he and a member of the Hapsburg Group met with lawmakers on the Senate Foreign Relations Committee.

"[Hapsburg Group member] did well, reading off our talking points," Sager wrote. That member is most likely former Italian Prime Minister Romano Prodi, who was visiting Washington and met with lawmakers that month. "The Republicans especially were quite [Tymoshenko] heavy, with one [senator] dwelling a bit on it," Sager continued.

He was referring to Yulia Tymoshenko, the former Ukrainian prime minister who was Yanukovych's rival during the country's 2010 presidential election. Tymoshenko was tried and jailed in 2011 after the Ukrainian government convicted her of abuse of power. The news drew criticism from human-rights groups and countries including the US, the UK, Germany, Italy, and Spain, which said the Yanukovych government’s conviction of Tymoshenko was politically motivated.

Sager wrote in his March 2013 email to Friedman that although Republicans asked questions about the Tymoshenko case, "[Hapsburg Group member] was solid … urging inclusion, a 'vigilant' Russia, trade opportunities, etc. PJM later said he had received two calls right after the meetings, praising [Hapsburg Group member]."

"PJM" is most likely a reference to Manafort, whose full name is Paul J. Manafort.

Sager said he met with "PJM" following the meeting with lawmakers.

Prosecutors also submitted a second memo to the court, this one sent in April 2013 from Manafort to Yanukovych. The memo was titled "US Consultants — Quarterly Report."

The memo focused largely on describing the "considerable ground" Ukraine was gaining in "enhancing its relationship with the USG," or the US government.

"This is largely a result of building a comprehensive strategy that adopted issues of importance to the USG, and focusing on key and positive messages to better inform key members of the USG about Ukraine's objectives which are in alignment with the West," Manafort wrote.

He added that he had "organized and leveraged the visits of" two Hapsburg Group members "to make critical in-roads in how policymakers view Ukraine." The members are most likely Prodi and former Austrian Chancellor Alfred Gusenbauer.

Manafort wrote that the lobbying strategy for the first quarter of 2013 was to "heavily engage" with Congress and the US government to focus attention away from Tymoshenko and toward "positive key issues" Yanukovych’s government was addressing.

"One of the most critical goals that we have achieved during this quarter is to prevent the application of any sanctions against the [government of Ukraine] or its officials," he wrote, adding that he and the Hapsburg Group had accomplished that goal by "implementing key messages from the 'Engage Ukraine' strategy, many of which resonate with key US officials."