Hunter Biden case dismissed after president's pardon

A federal judge has dismissed the gun case against Hunter Biden after US President Joe Biden issued a sweeping pardon for his son.

US District Judge Maryellen Noreika closed the case the week before Hunter Biden was to be sentenced.

He could have faced up to 25 years in prison, although as a first-time offender he likely would have gotten far less time or avoided prison entirely.

Prosecutors opposed dismissing the case, arguing in court documents that a pardon should not wipe away the case "as if it never occurred".

Hunter Biden was convicted on three felonies after he lied on a federal form to purchase a gun in Delaware by saying he was not a drug user in 2018, a period when he has acknowledged being addicted.

The Justice Department special counsel is also opposed to dismissing a case filed in California after he failed to pay $US1.4 million ($A2.2 million) in taxes.

A federal judge in Los Angeles has not yet ruled in that case.

The president's decision on Sunday to go back on previous pledges and issue his son a blanket federal pardon for actions over the past 11 years has sparked a political uproar in Washington DC, drawing criticism from many Democrats as well as Republicans and threatening to cloud Biden's legacy as he prepares to leave office on January 20.

Hunter Biden was originally supposed to strike a plea deal with prosecutors last year that would have spared him prison time but the agreement fell apart after Noreika questioned unusual aspects of it.

The US president on Tuesday ducked questions on his decision to pardon his son, ignoring calls for him to explain his reversal as he was making his first presidential trip to Angola.

Dismissing shouted questions with a laugh during a meeting with Angolan President Joao Lourenco at the presidential palace, Biden said to the Angolan delegation "welcome to America".

Biden was not scheduled to take questions from the press during his trip, press secretary Karine Jean-Pierre told reporters on Monday, and he has largely avoided any interaction with reporters since president-elect Donald Trump's victory last month.

In June, Biden told reporters as his son faced trial in a Delaware gun case, "I abide by the jury decision. I will do that and I will not pardon him".

In July, Jean-Pierre told reporters: "It's still a no. It will be a no. It is a no. And I don't have anything else to add. Will he pardon his son? No."

In November, days after Trump's victory, Jean-Pierre reiterated that message: "Our answer stands, which is no."