He said: "I've just not got the heart for it any more and I don't see the point in going through the motions.
"I've had a lot of knockbacks in my time but this has nothing to do with injury.
"I just don't enjoy it anymore."
Alexis Sanchez and Gareth Bale headline a host of big names who will be absent from next summer’s World Cup
The Republic of Ireland edged their way into the World Cup play-off lottery after a priceless 1-0 victory in Cardiff
Few have left a greater mark on football than mesmerising midfielder and all-round gentleman Sir Bobby Charlton, who turns 80 on Wednesday.
Another World Cup qualifying bid ended in misery for Scotland after a 2-2 draw in Slovenia saw them miss out
Wales and the Republic of Ireland meet in Cardiff on Monday evening with the prospect of a trip to the
Wales and the Republic of Ireland meet on Monday night in their final game of the first round of 2018 World Cup qualifying.