ARACHI, Pakistan, Sept. 29 ・In a giant city of whirling contradictions, of donkey carts that share choking traffic with gleaming S.U.V.'s, of emaciated one-legged beggars and billboards for running shoes, a three-story banner fluttered from a building in the Azizabad neighborhood, calling for peace, for an end to terrorism, for calm. It is the government's position, the moderate one, and it vanishes from Karachi almost around the corner.

In every direction in this city of 12 million people, the largest city in a nation that has become a crucial but brittle ally in the United States' war on terrorism, there are cries and signs for Osama bin Laden, for the Taliban, for holy war.

In the downtown, not far from a KFC restaurant, a young man stood in traffic to sell color copies of Mr. bin Laden's picture. Near the teeming port on the Arabian Sea, someone had used a paintbrush to crudely spell out "CRUSH AMERICA" in foot-high black letters.

Outside the largest Islamic seminary in Pakistan, Jamiat-tul-Islamia, boys shouted "Death to America" and laughed, as though it were a game, and mechanics warned that they would put down their wrenches and hammers and answer their mullahs' calls for jihad when the first American bomb hits the first grain of Afghan sand.

This is one of the world's largest cities, but the language people use to discuss the current confrontation is as old as the desert. "Fourteen hundred years ago, infidels threw stones and garbage on our prophet," said Mustafa Kamal Uddin, 32, a body- and-fender man. Yet Allah, he said, was merciful and did not strike at those who offended him. Holy wars, he said, come about only when Allah has no other way to maintain justice, times like now. "That is why Allah took out his sword."

Karachi, with a history of political turmoil and corruption that goes back to the founding of modern Pakistan in 1947, has long been considered one of the world's most dangerous cities, before most people had ever heard of Osama bin Laden. Now, there is a feeling of dread in some and seething anger in others. In Karachi, the economic heart of Pakistan, with its many, many Dunkin' Donuts and McDonald's, religion may rule the future.

There are many wealthy and middle-class Pakistanis here, people who support the alliance with the United States, who fear a rise in fundamentalist religion that, they say, could transform their country.

But there seem to be many more in Karachi who would welcome it, who in choosing sides would choose Mr. bin Laden in a heartbeat, because they see him as a hero of Islam.

"We don't want to become Afghanistan, and we think Pakistan will become like Afghanistan," said Nasreen Jalil, a former senator who lives in Karachi and is a member of the powerful Muttahida Qaumi Movement.

Politics here has been an often bloody process. But the standoff between the United States and the Taliban could have a far more drastic influence than any assassination or bombing in the past.

Even Ms. Jalil opposes American military action because of what could happen here if it is bungled.

"From the mosques, they are saying that this is a war on Islam," she said. "They think bin Laden is a symbol of Islam. It's mostly just talk, but peoples' emotions are heightened, and it could take a different turn. The people are not thinking. In the name of religion, they become oblivious to everything else."

With many high-ranking officers in the military aligned with the fundamentalists in this city ・and in the country that stretches northward from its port ・there seems little doubt who would win if a majority of the population adopts the fundamentalists' argument that this is a war between Islam and Christianity. "I don't know who would be able to control it," Ms. Jalil said. "We mustn't go back to the Stone Age."

Newspapers in Karachi have promised yet more "Death to America," and warned that the attacks in New York and Washington were a trick by the Jews to plunge the United States and Islam into war.

Some on the streets said they were sorry for the Americans, but said the United States would only cause more tragedy by killing or arresting Mr. bin Laden without proof. Few people here believe that the United States has any proof and few would believe any proof submitted, anyway.

Mention dead firemen, and they counter with dead teenagers shot to death in Palestine. Mention dead civilians in the World Trade Center, and they speak of children killed by American bombs in air strikes on Afghanistan and Iraq.

"They are terrified, and we are also terrified," said Dr. Abdurrazzak Sikander, principal of the Jamiat-tul- Islamia seminary in the Binori Town section, which draws students from many Islamic countries but especially from Pakistan and Afghanistan.

The United States has demonized Islam, Dr. Sikander said. "We give respect to Jesus, to Moses ・we even name our daughters after Mary," he said. But after the World Trade Center disaster, the United States has persecuted many followers of Islam, for no other reason than their facial hair, he said. "Everyone with a beard is called a terrorist," he said.

Like others here, he believes that the United States has not produced proof of guilt in the attacks.

If the mastermind behind the attacks is Mr. bin Laden, the United States must share the blame, people here said. It was the United States' presence in Saudi Arabia, they argue, that created Mr. bin Laden.

"But he didn't do anything," said Muhammad Khalid, who was praying at the seminary. Like many here, he reduces the confrontation to a political move by the United States to justify attacking Islam. "Bin Laden is Islam," said Mr. Khalid. "He represents Islam. Muslims are not in fear. They are all over the world."

Inside the quiet grounds of the seminary, Mufti Imdad Ullah said there were only two ways to deal with an enemy.

"Dialogue, or eliminate your opponent," he said. But even if you kill your enemy, he warned, "his race will remain, his people will remain."

At the headquarters of the Muttahida Qaumi Movement, Ms. Jalil, the former senator, contemplated a Karachi under a Taliban-like rule, where women have no rights.

She carefully covered her head before she was photographed. "Or they will say I am not a good Muslim," she said.

Everyone here seems to have a strong opinion about the United States, Pakistan, Afghanistan, the Taliban, Mr. bin Laden, all of it ・all, it seems, except a young man named Shahid who is selling color copies of Mr. bin Laden's photograph. He is asked if he is a follower of the man.

"No," he said, "I'm just selling him."