Watch Donald Trump call Isis 'number one tricky'

In today's press conference sought to draw the discussion away from Russia's alleged possession of compromising information on him, and focus on the mutual struggle against Islamic extremism.

"Isis, which, by the way, is number one tricky," he said, referring to the extremist group in typically unorthodox fashion.

Earlier Trump furiously denied allegations that Russia had compromising information on him, saying Moscow "never tried to use leverage on me".

Mr Trump condemned US intelligence agencies for allowing "fake news" to "leak" into the public, asking: "Are we living in Nazi Germany?"

An unsubstantiated report allegedly presented to Trump last week contained claims that the Kremlin has a dossier of compromising information on Trump, and key members of Trump's team secretly met Russian officials.