Pogba (right, in blue) has captained France's Under-16 team
Manchester United say they will take legal action against Le Havre unless they stop making allegations about the transfer of 16-year-old Paul Pogba.
The French club have this week repeated claims that United offered financial inducements to Pogba's family in order to lure the teenager to Old Trafford.
But United are satisfied the transfer was completed within Fifa guidelines.
"Manchester United is ready to defend any claim brought against it by Le Havre at Fifa," said a club statement.
Fifa, world football's governing body, says it has received no complaint about United's signing of the 16-year-old French midfielder.
And the Old Trafford club wrote to Le Havre on Monday warning the French side against making further accusations.
"In response to the wholly unfounded comments widely reported in the media of Le Havre AC President, Jean-Pierre Louvel, Manchester United wish to categorically confirm that as a matter of club policy and in accordance with the applicable football regulations, we do not offer inducements to the parents of players who sign for the club such as monetary payments or the purchase of houses," added a United statement.
The matter is with our lawyers right now and it is up to them what we do in regard to Fifa. But I can assure you we fully intend to defend our club's interests
Le Havre's managing director Alain Belsoeur
"Manchester United have written to Le Havre AC to put it on notice that action will be taken if such allegations are repeated in relation to the transfer of Paul Pogba.
"Manchester United is entirely satisfied that the transfer of Paul Pogba has been conducted in accordance with the regulations set down by the world governing body, Fifa.
"It is to be noted that all contractual documentation relating to the player's registration with the club has already been fully ratified by the Football Association and the Premier League."
Le Havre, though, have revealed that their legal team is preparing a case to take to Fifa.
"The matter is with our lawyers right now and it is up to them what we do in regard to Fifa. But I can assure you we fully intend to defend our club's interests," their managing director, Alain Belsoeur, told BBC Radio 5 live.
The French Football Federation has yet to release Pogba's international clearance certificate, meaning the player is unable to play for United's first team, academy or reserve sides.
The English Football Association has raised the matter with Fifa, after receiving a request from the Premier League champions, and its player status committee is now looking into the matter.
Belsoeur added: "When things are done properly in football, transfers between clubs in different countries are cleared by both the local association and the new association. That has not happened in this case."
Yet the player's agent, Gael Mahe, insisted United had done everything by the book.
"It is important for Paul, his family and for Manchester United to clear up this false information," he told BBC Sport.
"Manchester United just paid the player, there was no compensation for the parents.
"Most importantly of all, he did not have a contract with Le Havre, not even a scholar's contract, so the player did not breach a contract.
"Manchester United will compensate Le Havre for the two years he had with them. Paul is very happy at Manchester United. They have very high performance training and facilities - you cannot even compare Le Havre."
Pogba is one of the most highly-rated teenagers in France and has captained his country at Under-16 level.
Le Havre have an outstanding reputation in developing young players, having nurtured Real Madrid's Lassana Diarra, Wigan's Charles N'Zogbia and Atletico Madrid's Florent Sinama-Pongolle, who moved from the French club to Liverpool, before going to Spain.
Players from European Union countries are able to move to Britain on academy or scholarship contracts at 16, and to sign full professional contracts at 17.
By signing a player under the age of 18, the buying club minimises the level of compensation the selling club will get.
Le Havre, who were relegated to the French second division last season, claim an agreement between the club, Pogba and his parents was in place for the player to stay until the end of the 2009/10 season.
In August the French club released a statement on their website - under the heading 'Manchester United steal Paul Pogba from HAC (Le Havre)' - which said: "Le Havre wishes to express its indignation regarding the dealings of Manchester United's directors in relation to the young Paul Pogba.
"The player and his parents refused to keep the arrangement because Manchester United offered very high sums of money to the parents of the (player) with the aim of obtaining the transfer of their son.
"At a time when numerous parties - including at European Union level, governmental (level), or within Fifa or Uefa - are speaking out against the 'trading of minors,' Manchester United does not hesitate to uproot a 16-year-old kid."
But United officials suggested that there was no contract for the 16-year-old to break, therefore the Red Devils could not be offering inducements to do so.
Le Havre repeated those allegations in the wake of a transfer ban imposed on Chelsea last week for a similar infringement of the rules.
Chelsea have been banned from signing any new players until January 2011 after the club was found guilty of inducing Gael Kakuta to break his contract with Lens in 2007.
Ian Dennis and Brian Alexander host a BBC Radio 5 Live special on the fall-out from Chelsea's transfer ban from 1900 BST on Tuesday.
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