"I have enjoyed every minute of representing my country. It's a sad day for me," said the Liverpool skipper.
"It was a very difficult decision to make. It's something I have been contemplating for a long time, not just since the end of the World Cup.
"I've had to take an awful lot of advice from people who are close to me - players that I still play with, ex-players who I played with a long time ago, managers who I played for years ago.
"It's been a really tough decision, certainly one of the toughest since I turned professional at 18."