Cork-born midfielder Liam Miller has signed a pre-contract agreement with Manchester United following a successful medical at the club's Carrington training ground yesterday.

Miller's move from Celtic to Manchester, the subject of sustained speculation in recent months, began to look more like a reality on Tuesday when United made an official approach to the player's representatives at Drury Sports Management (DSL) about an offer.

By Wednesday an agreement on personal terms had been reached, and yesterday Miller signed the agreement committing himself to a move south over the summer.

It is believed the 22-year-old has signed a five-year deal worth around £25,000 (€36,000) a week.

Miller could end up making his debut for the premier league champions on the club's summer tour of the United States where, last year, he first caught the eye of United boss Alex Ferguson.

The Corkman was initially omitted from the Celtic starting line-up for the friendly game with United there, but after coming on during the first half he performed strongly in a game dominated, and eventually won 4-0, by the English side.

Ferguson then watched the midfielder play for Celtic in the Champions League against Anderlecht. Again he stood out for the Scots, and it appears that Ferguson has been biding his time since for the transfer window to open so that he could formalise his interest in the player.

The move will be a terrible blow for Celtic and the club's manager, Martin O'Neill, who had spoken before Christmas of his hope that Miller and Shaun Maloney might establish themselves as "the backbone of the team" within the next 18 months.

There will be some questions asked, however, as to how O'Neill managed to allow a player who has long been so highly regarded both inside and outside the club to get to within six months of the end of his contract, at which point he became free to listen to offers from and agree deals with others.

And worse for the Glasgow club, because Miller will turn 23 next month they are not entitled to compensation under the current transfer rules.

Miller's representatives had been keen to agree a new deal with the Glasgow club last summer but, despite positive noises from the Celtic management, seemed incapable of getting the club to complete the formalities.

By November the tables appear to have turned, with Miller having impressed on his appearances for the club both in the Scottish Premier League and the Champions League.

At that stage O'Neill described talks with DSL as having gone "very well", but it may well be that the player's Dublin agents, Fintan Drury and Eamonn McLoughlin, were by then advising him to hold out until he could hear what other offers were on the table.

United made no official comment regarding the agreement yesterday.

A Celtic spokesman, however, issued a somewhat testy statement in which it was claimed Miller had been offered the chance to become "one of the best-paid young players in Scottish football history".

"We have had no information from Manchester United of any pre-contractual agreement," the spokesman claimed. "We made an extremely generous offer to Liam Miller. In fact, it was the biggest salary deal ever put to a young Celtic player who has come up through the ranks.

"The offer was made following detailed consideration of his contribution to the team in 16 starts this season, as well as on the basis of his long-term potential."

That potential had never been seriously doubted by anyone who has seen him play at club level or with a succession of Irish international underage sides. Those close to both O'Neill and Ireland manager Brian Kerr compared him to Roy Keane in terms of his strength, skills and approach to the game. Ferguson's decision to sign him suggests he, too, may see him as a long-term replacement for the 32-year-old.

At senior international level, too, he is widely seen as having the potential to provide the drive in central midfield that Keane brought to the team prior to his controversial retirement in the summer of 2002.

Up until last season, Miller was still a regular in the Irish under-21 side, which he captained on a number of occasions, but he was expected to make his senior debut in the friendly match against Canada at Lansdowne Road before injury forced him to withdraw.

At Old Trafford he will join not only Keane but also John O'Shea, giving Ireland its strongest representation in the club's first team squad for many years.

And in making the move from Celtic to the English club he follows in the footsteps of Paddy Crerand, Lou Macari and Brian McClair, all of whom went on to enjoy outstanding careers for the Manchester outfit.