The U.S. is blocking the Venezuelan government from paying for Nicolas Maduro's legal representation in the drug trafficking case he faces in New York, the deposed Venezuelan president's defence lawyer said on Wednesday.

Maduro and his wife, Cilia Flores, both pleaded not guilty on January 5 to drug trafficking charges that could land them in a U.S. prison for decades. They are jailed in New York awaiting trial.

In a letter addressed to U.S. District Judge Alvin Hellerstein, who is overseeing Maduro's case, defence lawyer Barry Pollack said the Treasury Department on January 9 granted an exception to U.S. financial sanctions on Venezuela, allowing the South American country's government to pay Maduro's fees, but revoked that permission hours later without explanation.

Pollack said "Venezuelan law and custom" require the government to pay the expenses of the President and First Lady.

"The government of Venezuela has an obligation to pay Mr Maduro’s fees, Mr Maduro has a legitimate expectation that the government of Venezuela would do so, and Mr Maduro cannot otherwise afford counsel," Pollack wrote in a letter dated February 20 but made public on Wednesday.

A spokesperson for the Manhattan U.S. Attorney's office, which brought the case, declined to comment. The Treasury Department did not immediately respond to a request for comment.

U.S. special forces captured Maduro and his wife, Cilia Flores, in a dramatic nighttime raid in Caracas on January 3, following months of pressure from U.S. President Donald Trump's administration on the socialist leader to step down. Prosecutors say Maduro abused his power to help drug traffickers throughout his 13-year tenure.

Since Maduro's capture, his former Vice President Delcy Rodriguez has been running Venezuela. Maduro said in his January 5 court appearance that he was still the country's legitimate president.

Pollack said Flores could still receive government funds for her legal fees. Her lawyer, Mark Donnelly, did not immediately respond to a request for comment.

Pollack is best known for representing WikiLeaks founder Julian Assange, who pleaded guilty to conspiring to obtain and disclose classified defence information.