President Joe Biden on Thursday revealed that two journalists privately told him they would have to leave the country if Donald Trump won the election because he has threatened to jail them.

Biden made the claim as he addressed wealthy donors in California and spelled out the dangers of a second Trump term.

He singled journalist Katie Couric who was among the audience.

‘Katie, there’s two of your former colleagues, not at the same network, told me personally that if he wins they have to leave the country because he’s threatened to put them in jail,’ he said.

Biden offered no further details.

Trump has already made clear he is ready to seek revenge on opponents if he wins in November. 

And he has clashed repeatedly with journalists trying to ask him difficult questions.

Biden said: 'We can't take anything for granted. Trump and his friends are trying to divide us.'

'I promised I wouldn't name them,' he said, before about 60 guests in the basement of multimillionaire developer and stem cell campaigner Bob Klein.

'It doesn't say much about political courage. It says what the state of the party is right now.'

Biden is on the third-day of his fundraising swing through California as he ramps up his reelection fight.

Earlier Thursday, he met the widow and daughter of Alexei Navalny, the Russian opposition leader who dies in a Siberian penal colony last week.

The meeting took place at San Francisco's historic Fairmont Hotel, which was briefly disrupted by protesters demanding a ceasefire in Gaza.

'Biden, Biden, you can't hide. We charge you with genocide,' they sang, as bemused guests around the hotel coffee shop looked on. 

Other events during his trip included a reception in Beverly Hills on Tuesday where donors spent as much as $250,000 to attend, and a dinner in the San Francisco home of Gordon Getty, son of oil tycoon J. Paul Getty, on Wednesday evening.

On Wednesday he also spoke with a high powered group of campaigners called the Climate Leaders Group in the drawing room of a Pacific Heights home.

'We have a crazy S.O.B. like that guy Putin and the others and we always have to worry about nuclear conflict but the existential threat to humanity is climate,' he told them. 

It comes as his administration plans more sanctions to punish Moscow for the death in a Siberian penal colony of Russian opposition leader Alexei Navalny. 

The Russian leader hit back a day later, telling Russian state TV with a mocking smile: 'We are ready to work with any president. 

'But I believe that for us, Biden is a more preferable president for Russia, and judging by what he has just said, I am absolutely right.'

Biden also used Wednesday's reception to ridicule former President Donald Trump, who has repeatedly claimed his plight - pursued by courts - is similar to Navalny's.

'You listen to some of the things this fella has been saying, comparing himself to Navalny saying this country has become a communist country, and he's being persecuted just like Navalny was persecuted,' he said.

'I don't know where the hell this comes from. 

'If I stood here 10, 15 years ago and said any of this you'd all think I should be committed.'

He spoke to an intimate gathering of about 25 people, sitting on chairs set out by book cases with books including 'Beyond Oil,' and 'Field Notes from a Catastrophe.'