The Trump-Russia saga has taken another twist after the revelation the president's longtime confidant, Roger Stone, made contact with a Russian national during the 2016 presidential election.

The man, who called himself Henry Greenberg, offered damaging information to Mr Stone about Hillary Clinton, Mr Trump’s presumptive Democratic opponent in the upcoming presidential election.

The meeting took place two months earlier than federal officials have said a counterintelligence operation was officially opened and before WikiLeaks began releasing hacked Democratic emails.

It came in the same time period as other episodes in which Russian interests approached the Trump campaign.

A few weeks earlier, Trump campaign foreign policy adviser George Papadopoulos was told in London that the Russians had dirt on Ms Clinton - two weeks before the sit-down between Donald Trump Jr. at Trump Tower with a Russian lawyer.

Greenberg, who did not reveal the information he claimed to possess, wanted Mr Trump to pay $2 million for the political dirt, Stone told the Washington Post.

“You don’t understand Donald Trump,” Mr Stone recalled saying before rejecting the offer. “He doesn’t pay for anything.”

Later, Stone got a text message from Michael Caputo, a Trump campaign communications official who arranged the meeting after Mr Greenberg had approached Mr Caputo’s Russian-immigrant business partner.

“How crazy is the Russian?” Mr Caputo wrote. Noting that Greenberg wanted “big” money, Mr Stone replied: “waste of time.”

Two years later, the brief sit-down in Florida has resurfaced as part of special counsel Robert Mueller’s sprawling investigation of Russian interference in the 2016 presidential campaign, according to Mr Caputo.

Mr Caputo said he was asked about the meeting by prosecutors during a questioning session last month.

Mr Stone and Mr Caputo, who did not previously disclose the meeting to congressional investigators, now say they believe they were the targets of a setup by US law enforcement officials hostile to Mr Trump.

Their interactions with Mr Greenberg mean that at least 11 Trump associates or campaign officials have acknowledged interactions with a Russian during the election season or presidential transition.

Ex-MI6 agent behind Trump Russia dossier breaks silence

Those interactions have become public a year and a half after a Trump spokeswoman said that no one associated with the campaign had communications with Russians, or other foreign entities.

Interviews and additional documents show that Mr Greenberg has at times used the name Henry Oknyansky. Under that name, he claimed in a 2015 court filing related to his immigration status that he had provided information to the FBI for 17 years.

Mr Greenberg also attached records showing that the government had granted him special permission to enter the United States because his presence represented a “significant public benefit.”

Mr Greenberg says he stopped his FBI cooperation sometime after 2013, and denied that he had been acting on the FBI’s behalf when he met with Stone.

There is no evidence that Mr Greenberg was working with the FBI during his interactions with Stone.

An FBI spokeswoman declined to comment, as did a spokesman for special prosecutor Robert Mueller - the man charged with investigating the Trump campaign's alleged collusion with Russia.

Singapore Summit: historic first meeting between Trump and Kim Jong-un Show all 20 1 /20 Singapore Summit: historic first meeting between Trump and Kim Jong-un Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim leave following their historic meeting AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim sign a document committing to peace between their nations, amongst other things EPA Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump holds up a document that both he and Mr Kim have signed AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un The two leaders reach out to shake hands for the first time AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim shake hands as they meet for the first time Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim walk off stage, following their historic meeting Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim take a stroll after their meeting on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim interrupt their stroll to talk to the media AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Kim and Mr Trump look out over a balcony at the Capella hotel, where they held their meeting on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump takes questions at the press conference following his meeting with with Mr Kim AP Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump appreciates the crowd in the press conference following his meeting with Mr Kim Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump travels to the Istana ahead of the summit with Kim Jong Un on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Kim Jong Un travels to the Istana ahead of the summit with President Trump on June 12 Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Kim poses for a photo with Singapore's Finance Minister Vivian Balkrishnan and Education Minister Ong Ye Kung ahead of the summit with Mr Trump Twitter/Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump shakes hands with Singapore Prime Minister Lee Hsien Loong, meeting on Monday June 11 in the Istana, Singapore's presidential palace AP Singapore Summit: historic first meeting between Trump and Kim Jong-un At a working lunch on Monday, Singapore's Prime Minister surprised Mr Trump with a birthday cake, in early celebration of his 72nd birthday later in the week EPA Singapore Summit: historic first meeting between Trump and Kim Jong-un US Secretary of State Mike Pompeo answers questions about the summit at a press briefing in Singapore on Monday, June 11 Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un US President Donald Trump arrives at the Paya Lebar Air Base in Singapore on June 10, two days prior to his summit with North Korean leader Kim Jong Un Reuters Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump and Mr Kim met on Tuesday June 12 in the Capella hotel on the island resort of Sentosa, just off the south coast of Singapore AFP/Getty Singapore Summit: historic first meeting between Trump and Kim Jong-un Mr Trump boards Air Force One following the summit AFP/Getty

Mr Trump and his allies maintain that the meetings were inconsequential, and there was no collusion.

It is not clear how seriously investigators are taking the Florida meeting. Mr Caputo said that prosecutors took an "intense" interest in the interaction during his questioning last month.

The Florida meeting adds another layer of complexity to Mr Stone’s involvement in the Russia probe.

For months, it has been clear that the special counsel has been scrutinising repeated claims by Mr Stone that he communicated with WikiLeaks via a back-channel source before the group’s 2016 release of hacked Democratic party emails.

Mr Stone - who long urged Mr Trump to run for president - has mooted the possibility he will be indicted, speculating that Mr Mueller might charge him with a crime unrelated to the election in order to "silence" him.

He said he anticipates that his meeting with Mr Greenberg could be used in an attempt to pressure him to testify against President Trump — something he says he would never do.