President Donald Trump will delay a second summit with Russian leader Vladimir Putin until next year, the White House announced Wednesday.

National Security Adviser John Bolton cited Special Counsel Robert Mueller’s investigation into Russian interference in the 2016 presidential election in a statement announcing the delay. The White House last week announced Trump had invited Putin to Washington for a meeting in the fall, a move that was criticized by both Republicans and Democrats.

“The President believes that the next bilateral meeting with President Putin should take place after the Russia witch hunt is over, so we’ve agreed that it will be after the first of the year,” Bolton said.

There’s no deadline for Mueller to wrap up his probe and he’s given no signal that he intends to complete it by the end of the year. Trump frequently refers to the election interference investigation as a “witch hunt.”

The president provoked an uproar at home with comments during his Helsinki summit with Putin last week that cast doubt on U.S. intelligence findings that Russia interfered in the 2016 election.