US President Joe Biden's son Hunter will plead not guilty to charges of illegally buying a gun when he was using drugs, his lawyer said Tuesday.

Hunter Biden, 53, was charged last week with two counts of making false statements when claiming on forms required for a 2018 gun purchase that he was not using drugs illegally at the time.

On Tuesday, Hunter Biden's lawyer, Abbe David Lowell, asked the judge presiding over the case in the eastern state of Delaware to hold the first court appearance by video conference instead of requiring his client to attend in person.

Hunter Biden currently lives in California.

"Mr. Biden understands both the charges against him and his rights… and we believe the Court can be assured of that fact by conducting this initial appearance by video," Lowell said in the letter to US Magistrate Judge Christopher Burke.

"Mr. Biden also will enter a plea of not guilty, and there is no reason why he cannot utter those two words by video conference," Lowell said.

"Mr. Biden is not seeking any special treatment in making this request," he added. "He has attended and will attend any proceedings in which his physical appearance is required."

Hunter Biden is also facing a third charge, based on the same statements, that he illegally possessed the gun during an 11-day period in October 2018.

If convicted on all three felony charges, he could face 25 years in prison, though in practice the offenses are seldom punished by any jail time.

The indictment came two days after Republicans in Congress opened an impeachment probe against Joe Biden, a Democrat, alleging that when the elder Biden was vice president he benefited financially from his son's foreign business dealings.

They alleged, without offering hard evidence, that while vice president in 2015-2016, Biden intervened to protect an allegedly corrupt Ukrainian energy company, Burisma, where Hunter Biden sat on the board.

The gun charges against Hunter Biden were filed by Justice Department special counsel David Weiss, who has been investigating him since 2018 over various allegations, mostly related to his overseas business deals.

A plea deal between Hunter Biden and Weiss, covering the gun charge as well as alleged tax violations, collapsed two months ago.

Hunter Biden is a Yale-trained lawyer and lobbyist-turned-artist, but his life has been marred by alcoholism and crack cocaine addiction and his indictment has cast a shadow over his father's campaign for reelection next year.