An aide to Donald Trump's lawyer claims the president "knew exactly what was going on" with efforts to pressure Ukraine into investigating former Vice-President Joe Biden and his son.

Lev Parnas told MSNBC he went to Ukraine to put pressure on officials on behalf of Mr Trump and his personal lawyer, Rudy Giuliani.

The alleged intention was to damage Mr Biden, a potential Democratic rival to Mr Trump in next year's US election.

President Trump denies involvement.

The US president also says that he does not know Mr Parnas - a Ukrainian-American businessman and Republican party donor who is facing separate charges of campaign finance violations.

BBC