WikiLeaks has denied a UK media report claiming Donald Trump’s campaign manager secretly met with Julian Assange in the lead-up to the 2016 US presidential election.

Paul Manafort travelled to the UK to visit Mr Assange at the Ecuadorian Embassy in London within days or weeks of being brought aboard Mr Trump’s presidential campaign, The Guardian newspaper reported Wednesday morning.

If confirmed, the meeting suggests a direct connection between the Trump campaign and WikiLeaks, which released tens of thousands of emails stolen by Russian spies during the 2016 election.

The campaign seized on the emails to undermine Trump’s rival, Hillary Clinton.

The Guardian, which did not identify its sources, claimed that Manafort visited Mr Assange in 2013, 2015 and “around March 2016” – the same month that Russian hackers began their effort to steal emails from the Clinton campaign.

Mr Assange’s Ecuadorian lawyer, Carlos Poveda, told The Associated Press the Guardian report was false.

WikiLeaks said on Twitter that it was “willing to bet The Guardian a million dollars and its editor’s head that Manafort never met Mr Assange.”

Manafort also denied ever meeting Mr Assange, saying he is considering his legal options over the report.

“This story is totally false and deliberately libellous. I have never met Julian Assange or anyone connected to him,” Manafort said through a spokesman.

“We are considering all legal options against The Guardian, who proceeded with this story even after being notified by my representatives that it was false,” he said.

Manafort’s statement came one day after US Special Counsel Robert Mueller’s office told a federal judge that the former Trump campaign manager breached his plea agreement by lying repeatedly to the FBI despite pledging to cooperate with the probe.

In the same court filing, Manafort denied lying, but both sides agreed the court should move ahead and set a date to sentence him for his crimes.

The Guardian cited two unidentified sources as saying Manafort first met Assange at the embassy in 2013, a year after Assange took refuge there to avoid being extradited to Sweden over sex crime allegations.

The Guardian said Manafort returned to the Embassy in 2015 and 2016, and said its sources had “tentatively dated” the final visit to March.

The report added that Manafort’s visit was not entered into the embassy’s log book and cited a source as saying Manafort left after 40 minutes.

There was no detail on what might have been discussed, but the report also claimed that an internal document written by Ecuador’s intelligence agency and seen by The Guardian contained Manafort’s name on a list of “well-known” guests at the embassy in 2013. The list, according to the newspaper, also mentions “Russians”.

The Trump campaign announced Manafort’s appointment on March 29, 2016, when he initially served as the convention manager tasked with lining up delegates for the Republican National Convention.

He was promoted to campaign chairman in May 2016.

Manafort pleaded guilty to conspiracy and witness tampering on September 14, almost a year after he was first charged and following his conviction by a jury in a separate but related case on eight tax and banking crimes.

-with AAP