Donald Trump's facing a backlash as he arrives back in the US following a summit with Vladimir Putin.
Democrats and Republicans have criticised Mr Trump for saying he trusts the Russian President more than his own intelligence services.
He also said there was no reason for Russia to meddle in the 2016 presidential election.
President Trump has since tweeted to say he has "great confidence" in the US intelligence services.
As I said today and many times before, “I have GREAT confidence in MY intelligence people.” However, I also recognize that in order to build a brighter future, we cannot exclusively focus on the past – as the world’s two largest nuclear powers, we must get along! #HELSINKI2018
— Donald J. Trump (@realDonaldTrump) July 16, 2018
Critics are calling the US president "weak" and "cowardly", while senior Democrat Chuck Schumer says a further explanation is needed.
Former CIA Director John Brennan says Trump's comments are nothing short of treason.
Donald Trump’s press conference performance in Helsinki rises to & exceeds the threshold of “high crimes & misdemeanors.” It was nothing short of treasonous. Not only were Trump’s comments imbecilic, he is wholly in the pocket of Putin. Republican Patriots: Where are you???
— John O. Brennan (@JohnBrennan) July 16, 2018