"Prayers are not to be sermons, speeches, position statements nor political posturing. They are humble, personal appeals to God," Warren wrote. His spokesman would not elaborate.
Evangelicals generally expect their clergymen to use Jesus' name whenever and wherever they lead prayer. Many conservative Christians say cultural sensitivity goes way too far if it requires religious leaders to hide their beliefs.
"If Rick Warren does not pray in Jesus' name, some folks are going to be very disappointed," Caldwell said in a recent phone interview. "Since he's evangelical, his own tribe, if you will, will have some angst if he does not do that."
Advocates for gay rights protested Obama's decision to give Warren a prominent role at the swearing-in. The California megachurch founder supported Proposition 8, which banned same-sex marriage in his home state. Obama defended his choice, saying he wanted the event to reflect diverse views and insisting he remains a "fierce advocate" of equal rights for gays.
The Rev. Joseph Lowery, a United Methodist who is considered the dean of the civil rights movement, said he hasn't yet written the benediction for the Jan. 20 ceremony. But he said "whatever religion the person represents, I think he has a right to be true to his religion."
Caldwell, also a Methodist, said no one from the Bush team told him what to say in his 2001 and 2005 benedictions.
The Houston pastor said he had "no intention whatsoever of offending" people when he quoted from Philippians and delivered the 2001 prayer "in the name that's above all other names, Jesus the Christ." In 2005, he still prayed in Jesus' name, but added the line, "respecting persons of all faiths." In the 2008 election, Caldwell supported Obama.
Franklin Graham, son of evangelist Billy Graham, who was a presence at presidential inaugurations for several decades, said it's wrong to expect members of any faith to change how they pray in public.
"For a Christian, especially for an evangelical pastor, the Bible teaches us that we are to pray in the name of Jesus Christ. How can a minister pray any other way?" Franklin Graham said. "If you don't want someone to pray in Jesus' name, don't invite an evangelical minister."
Graham, who in 2001 stepped in for his ailing father, ended the invocation with, "We pray this in the name of the Father, and of the Son, the Lord Jesus Christ, and of the Holy Spirit."
The lawsuit, which claimed that inaugural prayer was an unconstitutional endorsement of religion, failed in federal court. It had been filed by atheist Michael Newdow, who separately sued to remove the words "under God" from the Pledge of Allegiance.
Billy Graham, now 90, didn't say Jesus' name during presidential inaugurations, but made obvious references to Christ.
At Richard Nixon's 1969 swearing-in, Graham prayed "in the Name of the Prince of Peace who shed His blood on the Cross that men might have eternal life." In 1997, for Bill Clinton's inaugural, Graham prayed "in the name of the Father, the Son and the Holy Spirit."
Leaders of other traditions with experience in interfaith work said they respected Christians who felt strongly that they should pray in Christ's name.
But they argued that a request for some modification is reasonable for a presidential inauguration, considering it's an event representing all Americans.
Imam Yahya Hendi, a Muslim chaplain at Georgetown University who travels to Muslim countries on behalf of the State Department, said that at interfaith events, he refers to Allah, or God, as "almighty creator of us all."
Rabbi Burt Visotzky, a professor at the Jewish Theological Seminary, the flagship institution of Conservative Judaism, said he invokes "God" for interfaith prayer.
"I know that for Christians, Jesus is part of their Trinity," said Visotzky, who has taught at Pontifical Gregorian University in Rome and at Protestant seminaries in the U.S. "For me as a Jew, hearing the name of a first-century rabbi isn't the worst thing in the world, but it's not my God."