If ever there was proof of the pressure cooker atmosphere in Washington DC it's this: the brain snap of CNN's anchor, Anderson Cooper.

Cooper has been forced to apologised for a "crude" remark he made during a live interview with the Trump backer, Jeffrey Lord.

"If [Mr Trump] took a dump on his desk, you would defend it," Cooper told Lord after the conservative political commentator defended Trump's description of the sacked FBI director James Comey as a "nut job" at a meeting with Russian officials.

President Trump fired Mr Comey while leading an investigation into alleged links between the presidential office and Russia.