Robertson said Tuesday that he worries about government funding religious groups that are outside the mainstream, such as the Church of Scientology, Hare Krishnas or the Unification Church.
``This thing could be a real Pandora's box,'' Robertson said on his ''700 Club'' broadcast. ``What seems to be such a great initiative can rise up to bite the organizations as well as the federal government.''
He added that it was ironic that he was lining up with liberal groups.
``You know, I hate to find myself on the side of the Anti-Defamation League and others, but this is, this gets to be a real problem,'' Robertson said, referring to the Jewish group that has expressed concerns about the Bush plan.
Robertson and his son, co-host Gordon Robertson, both said that government would be hard pressed to give grants to some religious groups and not others.
``I don't see how on a constitutional basis can you say, 'Well, this belief is OK, and this belief is not,''' Gordon Robertson said.
Pat Robertson could not be reached for further comment on Wednesday.
Asked about funding for non-mainstream religious groups when the plan was announced, Bush administration officials said that they would be eligible to compete alongside mainline religions.
Groups with religious ties have long received government funding, but to avoid constitutional problems, they have set up separate, nonreligious spin-offs. Under Bush's plan, they could compete for government grants directly, without altering the religious core of their programming.
Mainstream religious groups that currently provide social services have also voiced reservations with the plan.
Americans United for the Separation of Church and State, a vocal opponent, noticed Robertson's comments and argued that Bush's plan may be in jeopardy. ``This means Bush's plan is in enormous political trouble,'' said Barry Lynn, the group's executive director.
Asked about Robertson's comments, White House spokeswoman Claire Buchan said: ``We think this program is based on sound principles, and that it is the right thing to do, and the president is very committed to it.''