The ECB hope Pietersen can return to the England team on completion of a “reintegration process”.
Clarke, speaking at a joint press conference with Pietersen in Colombo, said: “Kevin will be engaged in a reintegration process which has already started today with a lengthy discussion with me.”
The reintegration programme will be overseen by England team director Andy Flower, beginning during the remainder of this month, and he will report back to the ECB hierarchy on when he thinks Pietersen is ready to return to the England team.
Clarke added: “Kevin has signed a contract with the ECB today. The central contract is for a period of time and, on conclusion of the programme, will be extended until the 30th of September this coming year (2013).”
Pietersen read out a statement in which he apologised for recent events and committed himself to playing for England in all formats until at least the 2015 World Cup.
He said: “I would like to take this oppourtuntity to apologise to my teammates, all the England supporters and the ECB for the situation that has arisen over the past months. Thankfully we can draw a line under it now and move forwards.”
Pietersen, who admitted in August that he had sent “provocative” messages to members of the South Africa team, was last month not included among the 10 centrally contracted players announced by the ECB for the 2012-13 season and left out of England's Test squad to tour India.
He is still hoping, however, that he can be added to the party to travel to India at the end of this month.
“It's been a horrible situation for all involved,” he said. “I am happy we are moving forward for a better result, I hope, for England cricket.”
Asked if he thought he may still travel to India, Pietersen added: “I hope so. I want to play for England as soon as I can.
“The process has started really well and I believe that, all being well, I'll be back in an England shirt as soon as possible.”