(CNN) - "Vote for biblical values this November 6."

That's the message from one of the most famous pastors in the U-S. In a full-page ad in major news publications, the Reverend Billy Graham is calling on voters to cast a ballot for their faith.

The 93-year-old evangelical preacher met Republican Mitt Romney for the first time last week at his home in North Carolina. But he has not endorsed any candidate for president. Instead, Graham's spokesman says the ads challenge Americans on how to vote, not who to vote for.

Graham has prayed with every American president since Harry Truman.