WASHINGTON (BLOOMBERG) - Former New York mayor Rudy Giuliani's associate Lev Parnas got US$1 million (S$1.36 million) from an account in Russia in September, a month before he was charged with conspiring to funnel foreign money into United States political campaigns, according to US prosecutors who asked a judge to jail him for understating his income and assets.

"The majority of that money appears to have been used on personal expenses and to purchase a home," prosecutors said in a court filing on Wednesday (Dec 11).

Parnas failed to disclose the payment to the government, prosecutors said.

The payment raises provocative new questions about the nature of the work Parnas and his associate Igor Fruman were doing and who they were doing it for. Much about what they did remains unclear.

The pair was charged, in part, with working on behalf of one or more Ukrainian government officials to seek the removal of then US ambassador to Ukraine Marie Yovanovitch. They have pleaded not guilty to all charges.

Bloomberg and other news organisations have also reported that Parnas was added to the legal team of Dmitry Firtash, a Ukrainian oligarch fighting extradition to the US.

Mr Giuliani and his lawyer didn't immediately respond to requests for comment. Mr Giuliani is also the personal attorney for President Donald Trump.

There was little detail or explanation about the source or purpose of the payment to Parnas in the court filing.

Prosecutors said the money was sent to an account in the name of Parnas' wife, Mrs Svetlana Parnas. It appeared "to be an attempt to ensure that any assets were held in Svetlana's, rather than Lev's, name", prosecutors claimed.

The payment came the same month that Parnas and Fruman received the first of two requests for documents from congressional committees investigating the Trump administration's actions in Ukraine.

The pair initially refused to comply with the requests, and were arrested days later on a jet bridge at Dulles International Airport near Washington DC, as they sought to board a plane with one-way tickets to Vienna.

Parnas' lawyer subsequently said his client was willing to comply with the congressional investigation.

Parnas, a US citizen who was born in Ukraine, could face at least five years in prison on the counts with which he has already been charged, but prosecutors have said he remains under investigation and will likely face more charges.

He and Fruman are also accused of using an unnamed Russian national as the source of funds for political donations to curry favour with state and federal officials for support in starting a retail marijuana business.

The government didn't say whether the same Russian was the source of the US$1 million payment in September.

Prosecutors asked the judge to revoke Parnas' bail, saying he also lied about his income.

While he presented varying pictures of his financial condition to the authorities on three different occasions, prosecutors say he never disclosed the US$1 million payment, or a US$200,000 escrow deposit he had made on a US$4.5 million Boca Raton property - and that he really received US$200,000 for his work on Firtash's legal team, not the US$50,000 he claimed.

"Parnas poses an extreme risk of flight, and that risk of flight is only compounded by his continued and troubling misrepresentations," prosecutors said.

The government was responding to Parnas' request for less strict bail conditions. He asked to be allowed some time each day outside his apartment while he is under home detention.

Parnas' lawyer, Mr Joseph Bondy, declined to comment and said he would respond to the prosecutors with his own filing.