Hunter Biden plans to change his not guilty plea in his federal tax case, his defence attorney said Thursday, just as jury selection was set to begin.

Defence attorney Abbe Lowell told the judge about Hunter Biden's plans to change his previous plea, just months after the U.S. president's son was convicted of gun charges in a separate case, but did not provide further details.

Hunter Biden, son of U.S. President Joe Biden, is facing misdemeanor and felony charges over what prosecutors say was a four-year scheme to avoid paying at least $1.4 million US in taxes while pulling in millions of dollars from foreign business entities. He is already confronting potential prison time after a Delaware jury convicted him in June of lying on a 2018 federal form to purchase a gun that he possessed for 11 days.

A last-minute plea would allow Hunter Biden to avoid a trial that was expected to put a spotlight on his foreign business dealings, which Republicans have spent years scrutinizing to accuse his father — without evidence — of corruption in connection with his son's work overseas.

The potential political ramifications of the trial just weeks before the presidential election may have faded somewhat since President Biden's July decision to drop out of the 2024 race. But the president is deeply concerned with the well-being of his son, so the trial is likely to weigh heavily on him in the final months of his five-decade political career.

Hunter Biden walked into the courtroom holding hands with his wife, Melissa Cohen Biden, and flanked by Secret Service agents. Initially, he pleaded not guilty to the charges related to his 2016 through 2019 taxes and his attorneys have indicated they will argue he didn't act "willfully," or with the intention to break the law, in part because of his well-documented struggles with alcohol and drug addiction.

WATCH | Republicans, Democrats use Biden's legal woes as political ammunition: 

GOP, Democrats use Hunter Biden conviction to score political points

Hunter Biden, the son of U.S. President Joe Biden, has been convicted of three felony gun charges. He is the first child of a sitting U.S. president to be convicted of a crime, and both Republicans and Democrats have seized on the moment to make points about the state of the justice system.

Hunter Biden had agreed to plead guilty to misdemeanor tax offences last year in a deal with the U.S. Justice Department that would allow him to avoid prosecution in the gun case if he stayed out of trouble. But the agreement imploded after a judge questioned unusual aspects of it, and he was subsequently indicted in the two cases.

His decision to change his plea Thursday came after the judge issued some unfavourable pre-trial rulings for the defence, including rejecting a proposed defence expert lined up to testify about addiction.

U.S. District Judge Mark Scarsi, who was appointed to the bench by former president Donald Trump, placed some restrictions on what jurors would be allowed to hear about the traumatic events that Hunter Biden's family, friends and attorneys say led to his drug addiction.

The judge barred attorneys from connecting his substance abuse struggles to the 2015 death of his brother, Beau Biden, from cancer, or the car crash that killed his mother and sister when he was a toddler.

The indictment alleged that Hunter Biden lived lavishly while flouting the tax law, spending his cash on things like strippers and luxury hotels — "in short, everything but his taxes."

Hunter Biden's attorneys had asked Scarsi to also limit prosecutors from highlighting details of his expenses that they say amount to a "character assassination," including payments made to strippers or pornographic websites. The judge has said in court papers that he will maintain "strict control" over the presentation of potentially salacious evidence.

Prosecutors could have presented more details of Hunter Biden's overseas dealings, which have been at the centre of Republican investigations into the Biden family often seeking — without evidence— to tie the president to an alleged influence peddling scheme.

The special counsel's team had said it wants to tell jurors about Hunter Biden's work for a Romanian businessman, who they say sought to "influence U.S. government policy" while Joe Biden was vice-president.

The defence accused prosecutors of releasing details about Hunter Biden's work for the Romanian in court papers to drum up media coverage and taint the jury pool.

Sentencing in Hunter Biden's Delaware conviction is set for Nov. 13. He could face up to 25 years in prison, but as a first-time offender, he is likely to get far less time or avoid prison entirely.