Washington: President Donald Trump cut short a television interview on Saturday in the US after being asked about his unsubstantiated claim that President Barack Obama had spied on him, reviving an incendiary charge even as his re-election campaign released its first advertisement taking aim at "fake news."

In the interview, which was timed to place a capstone on his first 100 days, Trump resurfaced allegations made in a bombshell Twitter post from early March that Obama had tapped his phones in Trump Tower, saying that while the former president had been "very nice to me," the two have had "difficulties."

"You saw what happened with surveillance," Trump said, declining to elaborate.

Asked by John Dickerson, the host of CBS' Face the Nation, "What does that mean, sir?"