A summary of the transcript of a telephone call between Donald Trump and Ukraine leader Volodymyr Zelenskiy confirms the US President did ask him to investigate Democrat Joe Biden.

It comes as the US House of Representatives is set to launch a formal impeachment inquiry into President  Trump over reports he sought to smear his political rival.

He said yesterday that he would release a transcript of his phone call.

Mr Trump also confirmed that he had withheld nearly $400m in US aid to Ukraine but denied he did so as leverage to pressure Mr Zelenskiy to initiate an investigation that would damage Mr Biden.

"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," Mr Trump said in the call, according to the summary provided by the Justice Department.

"Biden went around bragging that he stopped the prosecution so if you can look into it ... It sounds horrible to me," Mr Trump said, according to the memo.

The document is a summary of the phone call and not a verbatim transcript of the conversation.

President Trump has promised transparency in relation to the whistleblower whose complaints triggered the impeachment inquiry.

"I've informed them - all of the House members - that I fully support transparency on the so-called whistleblower information, even though it was supposedly second-hand information," he told a news conference tonight.

Earlier, President Zelensky insisted he had not been "pushed" by Mr Trump during the call in which the US President asked for the investigation of Mr Biden.

"We had - I think (a) good phone call. It was normal. We spoke about many things, and ... so I think and you read it that nobody pushed me," Mr Zelensky told reporters in New York, with President Trump sitting at his side.

The two leaders met on the sidelines of a United Nations General Assembly meeting.

The House of Representatives inquiry could lead to articles of impeachment in the House that could trigger a trial in the Senate on whether to remove Mr Trump from office.

Mr Trump told Mr Zelenskiy that Attorney General William Barr would contact him about re-opening the investigation into the Ukrainian gas company.

But Mr Trump did not ask Mr Barr to contact Ukraine, Justice Department spokeswoman Kerri Kupec said, and Mr Barr has not communicated with Ukraine about a possible investigation or any other subject.

Mr Barr, a Trump appointee, first found out about the conversation several weeks after it took place, Ms Kupec said.

Mr Trump has withstood repeated scandals since taking office in 2017. House Democrats had considered, but never moved ahead with, pursuing articles of impeachment over Mr Trump's actions relating to Russian interference in the 2016 US election aimed at boosting his candidacy.

Under the US Constitution, the House has the power to impeach a president for "high crimes and misdemeanors."

No president has ever been removed from office through impeachment. Democrats currently control the House and Mr Trump's fellow Republicans control the Senate.

The United States has been giving military aid to Ukraine since Russia's annexation of Crimea in 2014. The $391.5m in aid at issue in the current controversy was approved by the US Congress to help Ukraine deal with an insurgency by Russian-backed separatists in the eastern part of the country.

Mr Trump on Sunday acknowledged that he discussed Mr Biden and Mr Biden's son Hunter, who had worked for a company drilling for gas in Ukraine, with Ukrainian President Volodymyr Zelenskiy.

Mr Trump on Monday denied trying to coerce Mr Zelenskiy in the 25 July phone call to launch a corruption investigation into Mr Biden and his son in return for the US military aid.

Mr Trump has offered differing reasons for why he wanted the money for Ukraine frozen, initially saying it was because of corruption in Ukraine and then saying it was because he wanted European countries like France and Germany, not the United States, to take the lead in providing assistance to Kiev.

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The current controversy arose after a whistleblower from within the US intelligence community brought a complaint with an internal watchdog relating to Mr Trump's conversation with Mr Zelenskiy. Even though federal law calls for such complaints to be disclosed to Congress, the Trump administration has refused to do so.

Ms Pelosi yesterday said Mr Trump's actions had "seriously violated the Constitution," and accused his administration of violations of federal law.

The US Senate voted unanimously yesterday, with no objections from Mr Trump's fellow Republicans, for a resolution calling for the whistleblower's report to be sent to Congress.

The House was due to vote on a similar non-binding resolution today.

The Justice Department concluded that the whistleblower complaint did not need to be shared with Congress because the relevant law only covers conduct by intelligence officials, not the president, according to a legal analysis released by the department's Office of Legal Counsel.

US intelligence agencies and a special counsel named by the Justice Department previously concluded that Russia boosted Mr Trump's 2016 presidential election bid with a campaign of hacking and propaganda aimed at harming his Democratic opponent Hillary Clinton.