File Photo: Republican presidential nominee Donald Trump gives a thumbs up as his campaign manager Paul Manafort looks on during Trump's walk through at the Republican National Convention in Cleveland, U.S., July 21, 2016. (Xinhua/REUTERS)

WASHINGTON, Sept. 14 (Xinhua) -- Paul Manafort, U.S. President Donald Trump's former campaign chairman, pleaded guilty on Friday to reduced charges ahead of his second trial in Washington D.C. federal court. He will cooperate with Special Counsel Robert Mueller as part of guilty plea, prosecutor said.

Speaking at the beginning of the plea hearing in court, Prosecutor Andrew Weissmann said that Manafort has agreed to cooperate with investigators, as part of the 17-page plea deal.

The legal document requires Manafort to cooperate with Mueller's team "fully and truthfully." So far all the charges against Manafort are not related to Trump's 2016 presidential campaign.

"This had absolutely nothing to do with the President or his victorious 2016 Presidential campaign," White House Press Secretary Sarah Huckabee Sanders said in a brief statement after Manafort pleaded guilty.

"It is totally unrelated." she said.

Trump's personal lawyer, Rudolph Giuliani, said: "Once again an investigation has concluded with a plea having nothing to do with President Trump or the Trump campaign. The reason: the president did nothing wrong."

According to documents filed in court prior to the hearing, Manafort intends to plead guilty to two charges of the seven he faced at his second trial: conspiring to defraud the United States and conspiring to obstruct justice.

"Manafort cheated the United States out of over 15 million dollars in taxes," the document says, referring to the veteran Republican lobbyist's income in secret offshore accounts.

As part of the plea deal, the government plans to seize four properties, including a nearly 2-million-dollar house in Virginia owned by one of his daughters. The deal also calls for forfeiture of four financial accounts and a life insurance policy.

Local analysts say Manafort's cooperation with Mueller could provide new clues or evidence over the ongoing probe into alleged Russia meddling into the 2016 U.S. elections. However, the guilty plea would allow him to avoid the trial scheduled to begin later this month and last weeks before Nov. 6 midterm elections.