US House Speaker Nancy Pelosi. Photo: VCG

US House Speaker Nancy Pelosi on Friday urged the Trump administration to release a whistleblower complaint on the president's alleged inappropriate interactions with a foreign leader, an issue that continued to stoke speculations in Congress.

"We must be sure that the President and his Administration are conducting our national security and foreign policy in the best interest of the American people, not the President's personal interest," Pelosi said in a statement.

Trump reportedly communicated with a foreign leader and made an unspecified "promise," which an unidentified intelligence official considered so troubling that the official filed a whistleblower complaint in mid-August with the inspector general for the intelligence community, an independent watchdog.

Acting Director of National Intelligence (DNI) Joseph Maguire has been withholding the whistleblower complaint from Congress.

"The President and Acting (DNI's) stonewalling must end immediately, and the whistleblower must be provided with every protection guaranteed by the law to defend the integrity of our government and ensure accountability and trust," Pelosi said.

At least part of the complaint involved Ukraine, The Washington Post and The New York Times both reported, citing anonymous sources.

House Democrats, according to The Washington Post, have been probing a July phone call between Trump and Ukrainian President Volodymyr Zelensky to see whether Trump, and his attorney, Rudolph Giuliani, aimed to manipulate Kiev into helping his re-election campaign.

The Wall Street Journal, in an exclusive report Friday, said that Trump had urged Zelensky about eight times in the phone call to work with Giuliani in seeking information about Democratic presidential candidate Joe Biden's son, Hunter Biden, that could be damaging to Biden senior's campaign.

During a joint press availability in the Oval Office with visiting Australian Prime Minister Scott Morrison on Friday, Trump said that his conversations with leaders around the world were "always appropriate... at the highest level, always appropriate."

"It's just another political hack job. That's all it is," Trump said of the complaint.

Trump told reporters that it didn't matter what he discussed with Zelensky and that the phone call was "a beautiful conversation."

The president's response came amid heightened tensions between Congress and the White House over the scandal.

On Thursday, House Intelligence Committee Chairman Adam Schiff, a California Democrat, warned of possible legal action while lambasting Acting Director of National Intelligence (DNI) Joseph Maguire's decision to withhold the whistleblower complaint from the House committees.

"We do not have the complaint. We do not know whether the press reports are accurate or inaccurate about the contents of that complaint," Schiff told reporters. "We're determined to do everything we can to determine what this urgent concern is to make sure that the national security is protected."

Michael Atkinson, the inspector general, wrote in a letter to Schiff dated Sept. 17, "I set forth the reasons for my concluding that the subject matter involved in the Complaint's disclosure not only falls within the DNI's jurisdiction, but relates to one of the most significant and important of the DNI's responsibilities to the American people."