Keane's outburst came in the build-up to Sunderland's match with Wigan
Fifa vice-president Jack Warner has labelled Sunderland boss Roy Keane "callous" as their war of words over striker Dwight Yorke intensified.
Keane called him "a clown" when Warner wrote a letter blaming him for Yorke missing a Trinidad and Tobago match.
In a new letter on Friday, Warner again accused Keane of showing "disrespect."
And Warner, an advisor to the Trinidad Football Association, took a dig at Keane for walking out on the Republic of Ireland before the 2002 World Cup.
Warner is viewed as one of the most powerful men in world football and his importance can be traced back to England's failed 2006 World Cup bid, when three of England's five votes came from him.
The row began when Sunderland forward Yorke withdrew from his country's squad to face the United States.
Warner initially accused former Manchester United star Keane of being disrespectful for allegedly withdrawing Yorke from Wednesday's match.
But Keane retorted: "Yorke is retired. I've told Jack what I think of him and where to go. He's a clown, a disgrace."
But in his latest open letter to Keane, Warner said: "The disrespectful tone of your reported comments further demonstrates the total disrespect that you and others of your ilk have generally for players and officials from 'small' countries.
Warner says Trinidad and Tobago will not file an official complaint
"It is obviously difficult for you to accept the fact that someone from a 'small' country could rise to become a vice-president of Fifa."
Yorke, who played in the 1-1 draw with Guatemala at the weekend, was quoted in the Trinidad Express newspaper before he missed the 3-0 defeat by the US as saying that he was "feeling caught between a rock and a hard place with my club and my country".
The situation prompted Warner to send an open letter to the media, in which he said Keane's actions "will not endear you or Sunderland to such countries". He continued: "Your insensitivity and disrespect for countries such as Trinidad and Tobago are hereby noted."
However, Keane, speaking ahead of the Black Cats' Premier League match against Wigan on Saturday, stated: "Yorke has played one reserve game for us since busting a cheek recently.
"The agreement I had with the player was that he was not up to match fitness or speed and therefore wouldn't play in the match. He's 36 - he can't play two matches in a week.
"I love it when my players represent their countries at the highest level - I'm not like other managers in the Premier League and play silly games - but he's not fit and he says he's retired from international football anyway.
"Obviously, Mr Warner is making all these threats and a lot of them through the media but he doesn't really care about these players - he makes out he does but he doesn't.
"It's ridiculous. I'll be writing a letter back to Jack but - unlike him - I won't be giving it to the media. Basically, if he's the vice-president of Fifa, God help us all."
But in his follow-up letter responding to Keane's comments, Warner was even more critical.
"I chose to respond on a Fifa letter-head because that is a privilege afforded me owing to my said status and the fact that your callousness showed utter disregard for Fifa's regulations re the release of players for international duty. Regrettably, but not surprisingly, you did not grasp the message," wrote Warner.
He also referred to Keane's 2002 row with former Republic of Ireland boss Mick McCarthy.
"In closing may I remind you that a player's greatest honour is to represent his country in spite of the fact that you chose to walk away from yours during the 2002 Korea/Japan World Cup after publicly abusing your manager...indictment that you will no doubt be proud of up to today. Poor Sunderland."
Earlier, Keane warned that the player could face a reprimand too, saying: "Yorke has got to look at himself as well, mind.
"He's told me he's retired from international football about five times and then I switch on the TV and he's running about with the squad. I don't know if it's an ego trip or whether he likes the odd cameo.
"But I do know, for example, that we wouldn't have offered him a one-year deal this season if he'd said he was going to be playing for Trinidad. I'll be speaking to him.
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