Ex-Trump campaign manager Paul Manafort secretly paid unnamed former senior European politicians to lobby for Ukraine's previous pro-Russia government, a new indictment filed by special counsel Robert Mueller says.
Mr Manafort paid over €2m ($2.5m; £1.8m) to the ex-politicians, it says.
He has maintained his innocence in the face of Mr Mueller's investigations.
Mr Trump's ex-deputy campaign manager, Rick Gates, has admitted conspiracy and lying to investigators in a plea deal.
Mr Mueller is investigating claims of Russian political meddling in the US.
There are no allegations that either man colluded with Russia to influence the outcome of the 2016 presidential election, which is the main thrust of the justice department investigation.
Previously, Mr Manafort was charged with multiple counts of tax and bank fraud.
He faces new charges of conspiracy, money-laundering, failing to register as an agent for a foreign actor and making false statements.
His alleged payments to former senior European politicians were made in 2012 and 2013, the new indictment says.
He is also alleged to have created a group called the Hapsburg Group to give the former politicians' lobbying efforts the appearance of independent analysis.
The alleged group was managed by a former senior European politician named only as "Foreign Politician A" in the indictment.
The alleged paid lobbying was part of Mr Manafort's work for the Ukrainian government, a pro-Russian party, the Party of Regions, and its leader Viktor Yanukovych, who was president between 2010 and 2014, the indictment says.
Mr Manafort's work for Ukrainian pro-Russian political parties is said to have continued after Mr Yanukovych was overthrown and fled to Russia in 2014 following anti-government protests.
The indictment says Mr Manafort did not register as an agent of a foreign principal for this work as required by law.
He is also alleged to have hidden millions of dollars made from his Ukraine work in offshore accounts.
The new indictment was filed after Rick Gates pledged to co-operate in "any and all matters" with the Mueller inquiry.
Mr Gates, 45, is named in the new Manafort indictment as having worked to hide Ukraine income from the US authorities.
In a court appearance, Mr Gates admitted charges of conspiracy and lying to investigators.
He had previously had been indicted on more serious criminal counts, including bank fraud and money laundering.