Former Fifa vice-president Jack Warner has said in a TV address that he will reveal all he knows about corruption at world football's governing body.
Mr Warner, who said he feared for his life, also said he could link Fifa officials to general elections in his native Trinidad and Tobago in 2010.
He is one of the 14 people charged by the US over alleged corruption at Fifa.
Another top Fifa official and key witness, American Chuck Blazer, has admitted accepting bribes.
The admissions came in a newly released transcript of Mr Blazer's guilty plea from 2013, as part of a wide-ranging US criminal case that has engulfed Fifa and led president Sepp Blatter to resign.
The US justice department alleges the 14 people charged worldwide accepted bribes and kickbacks estimated at more than $150m (£97m) over a 24-year period. Four others have already been charged, including Mr Blazer.
Jack Warner: The US charge sheet
- Accused of racketeering, wire fraud, money laundering, bribery
- From the early 1990s, he allegedly "began to leverage his influence and exploit his official positions for personal gain"
- Allegedly accepted a $10m bribe from South African officials in return for voting to award them the 2010 World Cup
- Allegedly bribed officials with envelopes each containing $40,000 in cash; when one demurred, he allegedly said: "There are some people here who think they are more pious than thou. If you're pious, open a church, friends. Our business is our business"
Mr Warner, 72, resigned from all football activity in 2011 amid bribery allegations and later stepped down as Trinidad and Tobago's security minister amid a fraud inquiry.
A key figure in the deepening scandal, he said he had given lawyers documents outlining the links between Fifa, its funding, himself and the 2010 election in Trinidad and Tobago. He said the transactions also included Mr Blatter.
"I will no longer keep secrets for them who actively seek to destroy the country," he said in an address on Trinidadian TV on Wednesday evening entitled "The gloves are off".
Speaking to his supporters at a rally later the same day, he promised an "avalanche" of revelations to come.
Mr Warner, who denies the charges against him and faces extradition to the US, was released on bail after handing himself in to police in the Trinidad and Tobago capital of Port of Spain last week.
He resigned from Fifa's executive committee in 2011 amid allegations he had bribed his Caribbean associates.
At the scene: Ashley Semler, BBC News, Trinidad
A defiant Jack Warner was greeted as a hero, with cheers and loud, celebratory music at a rally for his political party, the ILP.
Ever the politician, he even held up a child for the cameras before taking to the podium.
He made multiple references to the international media that had descended on Trinidad and Tobago, saying he didn't realise that him spending a night in jail would make all of us come here - and assuring his constituents that we would be gone next week.
Mr Warner insists that he is innocent, and that he has always put the needs of his country first in both football and politics.
Mr Warner's address came hours after the details of Mr Blazer's 2013 plea bargain came to light, including the admission that he and other officials had accepted bribes in connection with the 2010 World Cup bid, which saw the tournament awarded to South Africa.
Separately on Thursday, South African police said they had opened a preliminary investigation into allegations that its national football association paid a $10m bribe to host the tournament - a claim the authorities deny.
Mr Blazer was the second highest official in Fifa's North and Central American and Caribbean region (Concacaf) from 1990 to 2011 - serving as general secretary while Mr Warner was president - and also served on Fifa's executive committee between 1997 and 2013.
Chuck Blazer's admissions
- He and others on Fifa's executive committee took bribes from 2004 until 2011 in exchange for backing South Africa to host the 2010 World Cup
- He agreed with a co-conspirator to facilitate a bribe in Morocco for its bid to host 1998 tournament, which was eventually awarded to France
- He and others accepted bribes in connection with broadcast and other rights for Concacaf's Gold Cup tournament in 1996, 1998, 2000, 2002 and 2003
- Other admissions include US tax evasion
Seven of the 14 men charged are top Fifa officials who were arrested in Zurich, Switzerland, as they awaited the Fifa congress last week. Two are vice-presidents.
In addition to the US case, Swiss authorities have launched a criminal investigation into how the 2018 and 2022 World Cups were allocated.
A law enforcement official quoted by Reuters news agency said the FBI, in addition to examining events during Mr Blazer's time at the helm of Concacaf, was also looking into how Fifa awarded Russia and Qatar the hosting rights for 2018 and 2022 World Cups. Both countries have denied any wrongdoing in the bidding process.
The authorities in Qatar say they are confident they will not be stripped of their right to host the 2022 tournament.
Meanwhile, UK Culture Secretary John Whittingdale has said England is ready to host the 2022 World Cup if Qatar is stripped of the tournament. There was a "strong case" for re-running the 2018 and 2022 bids if there is evidence of corruption, he added.
Mr Blatter resigned earlier this week in a surprise move, saying it appeared that the mandate he had been given to continue as president by the Fifa congress vote last Friday did "not seem to be supported by everybody in the world of football".
In his first comments since announcing he would step down as Fifa president, Mr Blatter - writing in Fifa's magazine The Weekly - said: "What matters to me more than anything is that when all of this is over, football is the winner."