FIRMLY ROOTED IN THE YEAR 600, AND PLANNING TO STAY THERE

Like other U.S. firms, Visa had been banned from doing business in Iraq because of international sanctions, which were lifted in May after more than a decade. But even before that, credit cards were extremely rare, making Iraq one of the biggest untapped charge markets in the world.

Although the potential seems vast, so are the challenges: Regular telephone service -- necessary for the machines that authorize purchases -- is still unavailable. Merchants are reluctant to pay Visa's fees. And Islamic leaders are counseling that usury and profits from loans are serious crimes under the Koran.

"Interest is like eating fire," said Sheik Mahmood Wisaya of the Al Gailani mosque, the biggest house of worship in Baghdad for Sunni Muslims.

Across town, the imam at the Mother of All Battles mosque, recently renamed the Mother of All Villages, eyed a shiny plastic Visa card and listened as an interpreter explained that it can be used to buy goods, which a customer pays for later -- along with a fee or interest.

"In Islam, this is not allowed," said the imam, Thaer Ibrahim Shammari, who also teaches at the Islamic College. "Every loan in which a profit is made will hurt the man who gets the loan. I don't approve of this company."

His father, Ibrahim, offered another reason why Visa may face obstacles in postwar Iraq. "I would boycott even the air if it came from the Americans," he said.

Still, Visa is bullish about its prospects, particularly in serving the thousands of U.S. officials, humanitarian aid workers, journalists and foreign business leaders who have flooded Iraq for the rebuilding effort. They will spend millions on hotels, restaurants and supplies in the coming years, and Visa is eager to pick up a chunk of the payments, which now must be settled in cash, usually Iraqi dinars or U.S. dollars.