At 4 a.m. yesterday, Marj Riley awoke, her spirits as dark as the early morning shadows in her Vienna bedroom. Through the blur of sleep just passed, she remembered that her country might be on the edge of war, and the only thing she knew to do was pray.

So she closed her eyes again, and called on her God to make her son-in-law Pete, an Army tank division commander in Saudi Arabia, "courageous, strong and wise." She prayed that President Bush and other Western political leaders, as well as Iraqi President Saddam Hussein, be open to a peaceful solution to the Persian Gulf crisis.

Her anxiety was eased, and she began to doze again. "Prayer does not always change the circumstances," she said later, "but it does change the one who prays."

In homes such as Marj Riley's, in grand cathedrals and makeshift chapels, on the street and in their cars, Americans with very little hope that war could be avoided were praying yesterday that it could.

And they sought assurance that if it couldn't, they would make it through the coming days of possible terrorism and probable deaths.

Prayer, often called the central activity of religious life, is the one exercise that men and women of all cultures have turned to in times of trouble. Americans, particularly, are a prayerful people. Nine out of 10 Americans say they pray.

During a multitude of prayer vigils this week, thousands of people have gone public and political with their prayers, asking that Bush be persuaded to allow economic sanctions more time to work.

Others, including Riley, have decided against lobbying God for any particular strategy. "There's just so much we do not know," Riley said.

Riley, 57, a homemaker and mother of three, went to high school during the Korean War and joined Holy Comforter, an Episcopal church, during the Vietnam War. A war in the gulf would be the first in which she has known someone in combat, she said, and on any given day, "I can get terribly afraid. I keep asking, What will I do if . . . ?"

Her 4 a.m. prayer hardly seemed enough, so after breakfast and while still at the table, Riley and her husband, Tom, prayed for peaceful resolution to the gulf crisis. After her husband left for work, Riley peeled oranges and cut up bananas to make a fruit plate for church, then drove to Holy Comforter for her weekly women's group, where she prayed again.

At noon, she walked into the church sanctuary and settled onto a kneeler, her eyes drawn to the multi-story stained glass window in front. Over the next hour, she and about 35 others read the comforting, familiar litanies of the Book of Common Prayer and offered up specific prayers for endangered friends and family, including Pete and Stuart, Rob and Ian, Bill, George and Monica.

Did she believe God would answer their prayers to keep those men and women safe? "God answers prayers," she said, "but God doesn't always answer yes."

Iraqi Muslims pray to their god, Allah, just as she prays to hers, she said, and they may pray for a different resolution. The age-old theological dispute over whose prayers God listens to doesn't bother her: "God has a plan that none of us knows."

After leaving Holy Comforter, Riley spent the rest of her day on the ordinary routines that in times like these, take one's mind off the awful. She did a little housecleaning, fixed her son a snack after he arrived home from school, and rummaged through a box of mail that has piled up since Christmas.

And every once in a while, she picked up her running conversation with the Almighty. Prayer is important not so much for what it will inspire God to do, she said, but for what it inspires her to do.

"You just have to do something," she said.