Following US evangelical leader Ted Haggard's recent confession of "sexual immorality", the disgraced pastor has agreed to a rehabilitation process that could last three to five years.

"I see success approximately 50 per cent of the time," said H.B. London, vice president for church and clergy at Focus on the Family, the conservative Christian ministry in Colorado Springs. "Guys just wear out and they can no longer subject themselves to the process."

Haggard was president of the National Association of Evangelicals and senior pastor of the 14,000-member New Life Church in Colorado Springs until last week, when a Denver man said Haggard paid him for sex nearly every month for three years and sometimes took methamphetamine during the encounters.

Although Haggard denied having sex with the man, he admitted buying meth but said he threw it away unused. He resigned from the NAE and days later was fired from his church.

London, who is not involved in Haggard's restoration, said the process will demand honesty from Haggard and determination from his overseers.

"It cannot be just a matter of friendship. It will have to become almost a confrontational relationship," he said. "You've got to confess your sins and you've got to have a group of people around you who will not let you whitewash the issue."

The process includes counselling, in groups and alone, and prayer. Each restoration is unique, with a programme tailored for the needs of the participant.

"From the Christian perspective, we think in terms of prayer, we think in terms of what we call godly counsel, where godly men who are clean themselves insert themselves in the life of the one who is struggling," London said.

The symbolic laying on of hands may also be a part of the recovery, London said.

"I'm sure there will be those who lay their hands on Pastor Haggard as an act of faith, calling on the act of God to restore and heal," he said. "The prayer can be therapeutic, the laying on of hands can be ceremonial."

One of the men who agreed to oversee the restoration, Focus on the Family founder James Dobson, has already withdrawn, citing a lack of time. The other two, Pastors Jack Hayford of The Church on the Way in Van Nuys, California, and Tommy Barnett of First Assembly of God in Phoenix, Arizona, declined to comment on the specifics of Haggard's programme.

It isn't clear whether Haggard will try to return to the ministry, at New Life or elsewhere. "He says that he has committed his life to God and that he is looking for direction as to where God can best use him," said Leonard Chessler, Haggard's lawyer and friend.