Jack Warner says he would "die first" before helping former FBI Director Louis Freeh investigate claims of bribery within Fifa.
Fifa's ethics committee appointed Freeh's agency to look into claims against Warner and Mohamed Bin Hammam.
Warner, who resigned as Fifa vice-president, said he would assist Fifa, but not Freeh because of his US links.
"I will die first. Not me. If Fifa wants me to cooperate I will do that but not with Freeh," said Warner.
"I'm not going to back a complaint made by an American and investigated by Americans and an attempt to put it on American soil because the complaint is from Miami.
"I don't back this farce," he told Bloomberg.
The 68-year-old's stance is such because both he and former Fifa presidential candidate Bin Hammam were suspended after executive committee member Chuck Blazer, an American, alleged that violations of Fifa's code of ethics occurred during a meeting organised by the two men in May.
Warner's remarks are in contrast to comments made by Fifa earlier on Tuesday, in which they claimed that former Concacaf federation president would appear as a witness in the continuing ethics committee investigation into bribery.
"Mr Warner will be investigated as a witness but not as an accused party," read a Fifa statement.
Fifa added that Warner had offered his support to the ethics committee.
Warner and Bin Hammam were accused of giving or offering bribes of £600,000 to Caribbean football associations.
They both denied any wrongdoing but were suspended on 29 May pending further investigation by the ethics committee.
After Warner quit on Monday, Fifa released a statement which stated that "as a consequence of Mr Warner's resignation, all ethics committee procedures against him have been closed and the presumption of innocence is maintained".
Fifa says Warner will be involved as a witness in the continuing investigation into the allegations against Bin Hammam and the Caribbean associations.
In his resignation statement on Monday, Warner said: "I am convinced, and I am advised by counsel, that since my actions did not extend beyond facilitating the meeting that gave Mr Bin Hammam an opportunity to pursue his aborted bid for the Fifa presidency, I would be fully exonerated by any objective arbiter."
Warner claimed he had been "hung out to dry" and that "gifts have been around throughout the history of Fifa".