Roy Keane has agreed to take up the offer of a testimonial match which will take place at Old Trafford on may th between his current club Celtic and former employers Manchester United.

The testimonial formed part of the deal which saw him leave United in November and although notoriously critical of testimonial games, Keane is expected to donate most of the proceeds to charity and has already declared his intention to release 1,000 free tickets to local Manchester schools and United supporters' clubs.

Although there is no indication which team Keane will play for, it would be no surprise if he donned the famous United shirt for one final time, even for only part of the game.

"I am grateful to Manchester United for awarding me a testimonial game and to Celtic for agreeing to participate in it," said Keane. "I look forward to returning to express my appreciation to the fans for the support that they had given me over the last 12 years."

Alex Ferguson added: "This is something that we wanted to do this season as Roy started the season with us. The supporters want to recognise the unbelievable contribution and success he had with Manchester United.

"He was a fantastic player and captain for me and I hope he gets the proper send-off he truly deserves. It will be fantastic night for everyone."

Keane left Manchester late last year after winning seven Premiership titles and four FA Cups in 480 appearances for United.

Celtic chief executive Peter Lawwell added: "Celtic FC is delighted to play in Roy Keane's testimonial match at Old Trafford. Roy was a magnificent servant to Manchester United for 12 years and I am sure he will forever be regarded as one of their greatest ever players. Clearly we are delighted to now have Roy here at Celtic.

"I am sure the atmosphere will be electric on the evening and it will be a fantastic occasion for fans of both teams, paying tribute to one of the greatest ever players to play the game."

Meanwhile Keane has admitted he will consider hanging up his boots at the end of the season even though he is contracted to stay at Parkhead for another year but fears a long-standing hip injury may come back to haunt him.

The 34-year-old said: "When I signed for Celtic I did say to them that it would be best for the club and myself to maybe look at things in the summer but they were quite keen for me to sign for the extra year, which I did eventually.

"But I will look at things in the summer and see how my hip is bearing up. I'm due to go back to the hip specialist in the summer. It's important to be fair to myself and the club if it is affecting me.

"I'll weigh it up then but there are no guarantees about next season, I have to say. Since having the surgery in 2002 I've regarded every season as a bonus but I've got to look at the long-term side of it and see what's best for me and my family.

"Over the last few months I've always put football first but come the summer I need to look at what's best for my family."