The White House has released details of a phone call between President Trump and his Ukrainian counterpart that has triggered a US impeachment inquiry.
It shows Mr Trump asked Volodymyr Zelensky on 25 July to investigate Democratic candidate Joe Biden, whose son worked for a Ukrainian gas firm.
Mr Trump denies withholding US military aid to Ukraine as leverage in a bid to smear his political rival, Mr Biden.
The Trump-Ukraine phone call is part of a whistleblower's complaint.
Reacting to the controversy on Wednesday morning at the United Nations General Assembly in New York City, Mr Trump said it was the "single greatest witch hunt in American history".
On Tuesday, Mr Trump promised that a "complete, fully declassified and unredacted transcript" of the 25 July call would be released.
But the details disclosed by the White House on Wednesday morning were notes of the conversation taken by US officials who listened in.
The July call occurred days after Mr Trump directed the US government to withhold about $391m (£316m) in military aid to Ukraine.
There is no discussion of that money in the memorandum released by the White House.
According to the notes, Mr Trump mentions to Mr Zelensky how Joe Biden, as US vice-president, lobbied Ukraine in 2016 to fire its top prosecutor, Viktor Shokin.
Mr Shokin's office had opened an investigation into Burisma, a natural gas company on which Hunter Biden was a board member.
Other Western officials had called for Mr Shokin to be fired because of the perception that he was soft on corruption.
Mr Trump is quoted as saying 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."
He continues: "There was a lot of talk about Biden's son, that Biden stopped the prosecution and a lot of people want to find out about that so whatever you can do with the Attorney General would be great.
"The other thing, there's a lot of talk about Biden's son.
"That Biden stopped the prosecution and a lot of people want to find out about that so whatever you can do with the 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."
Mr Zelensky says in response: "We will take care of that and we will work on the investigation of the case.
"On top of that, I would kindly ask you if you have any additional information you can provide us, it would be very helpful."
Thanking Mr Trump, Mr Zelensky said he stayed in the Trump Tower in New York City during his previous visit to the US.