TULSA, FEB. 28 -- Evangelist Oral Roberts will begin a marathon prayer and fast vigil March 22 that will last until he either gets the rest of the money he needs for a medical scholarship program or "God calls me home," he said in a letter mailed last week.

Roberts told recipients of the letter that he believes they will help him fulfill God's instruction to raise $8 million for the scholarships. Roberts has said God ordered him to raise the $8 million by the end of March, or he will die.

The evangelist wrote that he will ascend the Prayer Tower at Oral Roberts University to begin praying and fasting.

"If I go from there to Jesus, I will see you in heaven. But I believe that won't happen, because I believe our God will do this mighty thing and at the end of March, you and I will know the miracle has happened and the Gospel will go to the nations," he said.

The tower will be closed the week of Roberts' vigil in his personal prayer room atop the 100-foot building, Jan Dargatz of the Oral Roberts Evangelical Association said. She said Roberts has no specific schedule for his time in the tower.

In the letter, Roberts asks supporters to send prayer requests for him to take to the tower, to be with him in spirit on March 22 and to pray about sending $50 to the ministry. Roberts said he understands his revelation of God's message has caused problems for supporters. "And just as controversy raged over Paul, it's happening to us . . . . As you know, the news media have questioned our motives and mocked and held us up to ridicule for weeks now. They are saying that while it is noble to send medical missionaries to open up nations, I am a terrible person to use this to raise the $8 million it takes to give scholarships to the ORU medical students to carry out God's mandate," the letter read.

"I know as my partner, you've been hit also. And I thank you from the bottom of my heart for sticking by me . . . ."