US President Donald Trump has hit back at Robert De Niro after the Oscar-winning actor used an expletive to condemn him at the Tony Awards.

"Robert De Niro, a very Low IQ individual, has received to many shots to the head by real boxers in movies," President Trump tweeted. "I watched him last night and truly believe he may be 'punch-drunk'."

De Niro, who won the Academy Award for Best Actor for his portrayal of boxer Jake LaMotta in the 1980 film "Raging Bull," got a standing ovation at the Tony Awards on Sunday with his denunciation of President Trump.

"I'm going to say one thing – f*** Trump!" De Niro said, pumping his fists in the air.

"It's no longer 'down with Trump', it's 'f*** Trump!'" he told the crowd at New York's Radio City Music Hall honouring the best performances on Broadway.

The CBS television network, which was broadcasting the event live but with a delay of a few seconds, bleeped out De Niro's expletive.

President Trump defended himself against De Niro's attack by praising the economy under his watch.

"I guess (De Niro) doesn't realise the economy is the best it's ever been with employment being at an all time high, and many companies pouring back into our country," the president said. "Wake up Punchy!"

De Niro has attacked President Trump on previous occasions, describing him in 2016 as "blatantly stupid," "totally nuts" and an "idiot".