President Joe Biden held an emotional meeting with Alexei Navalny's widow and daughter in California and promised major new sanctions against Vladimir Putin and the Russian regime.

The president spoke privately with Yulia and Dasha Navalnaya in a suite at the Fairmont hotel in San Francisco.

White House officials said he shared his condolences for the death of Putin's top critic and opposition leader in a Siberian penal colony last week.

Biden hugged Yulia and promised that her late husband's legacy would live on as Moscow ramped up its threats of nuclear attacks on the West.

The meeting came hours after Biden publicly called Putin a 'crazy S.O.B.' in the wake of Navalny's death at the age of 47. 

After the meeting Biden spoke briefly in the garage of the hotel as he got into is vehicle.

The president said: 'He (Navalny) was a man of incredible courage. It's amazing how his wife and daughter are emulating that.

'We'll be announcing the sanctions against Putin, who is responsible for his death, tomorrow.

'One thing Yulia made clear to me is that she's going to continue to fight. We're not letting up.'