WASHINGTON -- Paul Manafort, the longtime U.S. lobbyist and former election campaign chairman for President Donald Trump, is expected to plead guilty to charges of conspiracy and witness tampering, just days before his second federal trial was scheduled to begin.

Manafort was scheduled to appear later on September 14 in U.S. District Court in Washington, D.C., where court documents indicated that he was reversing his position on the charges.

While such a move suggests a plea deal with Special Counsel Robert Mueller, the court filings do not indicate where there is an agreement with prosecutors to cooperate with Mueller's sprawling investigation into the Trump campaign, and Russian interference in the 2016 election more broadly.

Jury selection had been set to begin on September 17 in the second trial for Manafort, who was convicted last month in Virginia federal court on bank and tax fraud charges.

That case was the first brought by Mueller to go to trial, and the guilty finding by the jury -- on eight of 18 charges -- was a significant victory for Mueller’s team.

Manafort's lawyers had earlier indicated that they were prepared to go to trial, so the last-minute guilty plea suggested that Manafort might also agree to cooperate with Mueller's prosecutors.

As with in the Virginia case, the trial in Washington focused on criminal charges that largely predated Manafort’s time with Trump’s 2016 presidential campaign.

Manafort served for several months on the campaign, including as campaign chairman, until he was fired in August 2016, amid revelations of the scope of his consulting and lobbying work for Ukrainian politicians, including then-President Viktor Yanukovych.

The main focus of prosecutors in the second trial was the allegation that Manafort lobbied on behalf of Ukrainian politicians without registering under the Foreign Agents Registration Act.

The charge of witness tampering -- formally called obstruction of justice -- was added earlier this year after prosecutors alleged the Manafort and his longtime Ukrainian point man, Konstantin Kilimnik, had contacted potential witnesses after Manafort had been indicted in an effort to persuade them to change or coordinate their stories when discussing the case with prosecutors.

A guilty plea helps Manafort avoid the possibility of additional prison time in the event that the Washington jury were to have convicted him.