WASHINGTON (BLOOMBERG) - President Donald Trump has said he will release the transcript of a July phone call with Ukrainian President Volodymyr Zelenskiy, seeking to defuse a ballooning controversy over allegations he sought foreign help to smear a political rival.

Trump acknowledged earlier on Tuesday (Sept 24) that he had ordered a halt to US military aid to Ukraine, claiming he was frustrated that Europe wasn't also contributing to the country's fight with Russia-backed separatists.

The July 25 call with Zelenskiy is the focus of a congressional investigation into whether Trump pressured Ukraine to re-open an investigation linked to the family of former vice-presient Joe Biden in exchange for restoring the aid.

Trump said he will release a complete, unredacted transcript of the call on Wednesday.

US stocks pared declines after Trump tweeted the news.

The call is also part of a mysterious whistle-blower complaint from an unidentified intelligence official. Congressional Democrats have demanded a copy of the complaint, but the acting director of national intelligence, Joseph Maguire, has refused.

Trump did not address the complaint in his tweets.

The chairman of the House Intelligence Commitee, Democrat Adam Schiff of California, said on Wednesday that the whistle-blower has asked to testify to his panel.

Biden is scheduled to address reporters on the matter on Tuesday. His campaign said earlier that he would back impeaching Trump if the White House refuses to comply with congressional demands for information about his interactions with Ukraine's president.

Trump is expected to meet with Zelenskiy on the sidelines of the UN General Assembly on Wednesday. The Ukrainian leader said in an interview with Voice of America on Tuesday that he expects the meeting "will be very warm."

Trump ordered his acting chief of staff to delay sending US$400 million (S$550 million) in military aid to Ukraine at least a week before he spoke to Zelenskiy, a person familiar with the matter said Monday night.

Trump said on Tuesday that he withheld the aid over a previously unknown dispute with Europe.

"My complaint has always been - and I'd withhold again, and I'll continue to withhold until such time as Europe and other nations contribute to Ukraine," Trump said as he arrived at United Nations General Assembly. "Because they're not doing it. It's the United States. We're putting up the bulk of the money and I'm asking why is that."

The European Union says it's provided more than €15 billion (S$22 billion) in grants and loans to Ukraine since 2014 to help the country fight corruption and reform its institutions.

'ANTI-TANK WEAPONS'

Later at the UN, Trump complained that France and Germany aren't "paying payment" to Ukraine.

"You know, President Obama used to send pillows and sheets," he said. "I sent anti-tank weapons and a lot of things to Ukraine."

German Chancellor Angela Merkel's government has helped lead efforts to broker peace in eastern Ukraine as part of the 2015 agreement with Russia known as the Minsk accord.

But she has steadfastly opposed shipping weapons to Ukraine, insisting the move would only compound an armed conflict with Russian forces. Only compliance with the Minsk agreement will stop the fighting, Merkel has said.

On Monday, Trump said he didn't ask Zelenskiy for an investigation of Biden in exchange for the military aid.

The aid was restored earlier this month, and Trump has not previously explained why it was halted. At the UN on Monday, he said he had discussed "corruption" with Zelenskiy in the July 25 call.

"It's very important to talk about corruption," he said. "If you don't talk about corruption, why would you give money to a country that you think is corrupt?"

Trump's order to acting chief of staff Mick Mulvaney to halt the aid was reported earlier on Monday by the Washington Post. Asked about the episode, Hogan Gidley, a White House spokesman, said, "The media pushed the Russia lie for almost three years with no evidence, and now they are doing it all over again. These allegations are completely false, but because the media wants this story to be true so badly, they'll once again manufacture a frenzy and drive ignorant, fake stories to attack this president."

IMPEACHMENT MOMENTUM

On Monday, Trump's personal lawyer Rudy Giuliani said he couldn't rule out the possibility that the president threatened to cut off aid to Ukraine over calls for an investigation into largely discredited allegations against Biden and his son Hunter Biden.

Three House committees are investigating whether Trump used the withholding of military aid as leverage, and several more Democrats have come forward to demand for impeachment proceedings. The chamber's Democratic caucus will meet on Tuesday afternoon to discuss the whistle-blower's complaint, according to a person familiar with the matter.

And seven freshmen Democrats who had not expressed support for impeachment wrote in a Washington Post op-ed published Monday night that "if these allegations are true, we believe these actions represent an impeachable offence."

The seven representatives are Gil Cisneros of California, Jason Crow of Colorado, Chrissy Houlahan of Pennsylvania, Elaine Luria of Virginia, Mikie Sherrill of New Jersey, Elissa Slotkin of Michigan and Abigail Spanberger of Virginia.

TRUMP HOSTILE AT UN

At the UN, Trump grew hostile as reporters questioned him about the matter at the meeting with Polish President Andrzej Duda.

"Joe Biden and his son are corrupt," he said. "If a Republican ever did what Joe Biden did, if a Republican ever said what Joe Biden said, they'd be getting the electric chair by right now."

Trump alleges that as vice-president, Biden pressured Ukraine to fire its prosecutor general in 2016 in order to stop an investigation of a company connected to Hunter Biden.

It's true that on behalf of the Obama administration, Biden demanded that Ukraine oust its top prosecutor, Viktor Shokin, who had been accused of corruption by his deputy. Shokin had investigated a company called Burisma Holdings, where Hunter Biden sat on its board and received substantial compensation.

Biden said in a 2018 event at the Council on Foreign Relations that he had threatened to withhold US$1 billion in US loan guarantees from Ukraine unless its leaders dismissed Shokin. The Ukrainian parliament wound up voting to remove the prosecutor.

But by the time the Obama administration joined with other Western nations to force Shokin's removal, the Burisma investigation had been long dormant, Shokin's former deputy Vitaliy Kasko said in an interview with Bloomberg News earlier this year.

Trump said that in his call with Zeleskiy, "I did not make a statement that you have to do this or I'm not going to give you aid." Trump said he's still thinking about releasing a transcript of the call, though he's expressed misgivings about setting a precedent for conversations that are usually confidential.

"I may do it because it was a very innocent call," he said. "I hope you get to see it, and I hope you get to see it soon."