Trump addresses his communication with Ukraine leader on Biden

US president Donald Trump repeatedly prodded Ukraine's president to look into Democratic rival Joe Biden, according to a rough transcript summarising a call between the two leaders.

In the July 25 call, Mr Trump raised unsubstantiated allegations that the former vice president sought to interfere with a Ukrainian prosecutor's investigation of his son Hunter.

According to the memo, Mr Trump said to Ukrainian president Volodymyr Zelenskiy: "I heard you had a prosecutor who was very good and he was shut down and that's really unfair.

"A lot of people are talking about that, the way they shut your very good prosecutor down and you had some very bad people involved."