The Trump administration has released details of a phone conversation in July that has triggered a US impeachment inquiry against the president.
The US president has asked the Ukrainian leader to look into corruption claims involving the son of Joe Biden, Mr Trump’s possible rival in next year’s presidential election.
But Mr Trump has denied withholding US military aid to Ukraine as leverage.
The Trump-Ukraine phone call has been brought forward because of an informer’s complaint.
In the phonecall Mr Trump discusses with his newly elected Ukrainian counterpart, Volodymyr Zelensky, the 2016 removal of a prosecutor, Viktor Shokin.
The US president says in the call: “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.”
He continues: “The other thing, there’s a lot of talk about Biden’s son, that Biden stopped the prosecution [of Mr Biden’s son] and a lot of people want to find out about that so whatever you can do with the [US] Attorney General would be great.
“Biden went around bragging that he stopped the prosecution so if you can look into it… It sounds horrible to me.”
In answer to it Mr Zelensky says: “We will take care of that and we will work on the investigation of the case.”
Thanking Mr Trump, Mr Zelensky then thanked Trump and said he stayed in Trump Tower in New York City during a previous visit to the US.
According to the notes, during the call, the US president also asksed Mr Zelensky to work with US Attorney General William Barr and Mr Trump’s personal lawyer, Rudolph Giuliani, to look into the matter.