As a minority in their community, Pakistani Christians once only encountered tolerance among their Muslim neighbors and friends.
But that's changed in the weeks since the Sept. 11 terrorist attacks on the U.S. Now they've come face-to-face with hostility, tension and fear.
Many Christians in Pakistan say close Muslim friends now keep their distance. And if any fighting starts over the border, some are worried the worst could happen.
"Every day we hear threats from Muslims," said a high school teacher who pleaded to be identified only as Anwar. "Sometimes, we don't sleep. We are terrified that if they attack Afghanistan, we may be killed."
Sabir Yaqoob, 28, who teaches physics at a different high school, believes that President Bush unleashed fury with an early reference to a "crusade," which the White House later said was not meant to imply a religious war against Islam. The White House said Bush used the term in the sense of a "broad cause" and meant no offense.
"He said it, and that's enough." Yaqoob said. "It is what the fundamentalists heard. Crusade means a clash between Muslims and Christians, and that is what we are all afraid of."
His friend, Moussa Sadiq, 35, a phone company employee, broke in.
"Our old friends who used to eat with us, sit together morning and evening, they tell us they will attack us if there is fighting," he said. "They will be the first to kill us."
At an unmarked, old chapel called Sacred Heart Catholic Church in Quetta, Pakistan, the small but fervent congregation has been praying for America to defeat terror without creating Christian martyrs.
Sacred Heart is one of two Catholic churches in Quetta. There is also an Anglican church. Officially, Christians number 4 million in Pakistan, 3 percent of the population. Church groups say the total may be 8 million.
Although a heavy majority of Christians are in Punjab and Sindh, farther from Afghanistan where feelings run cooler, the fear seems widespread.
Yaqoob said he was surprised, and worried, at the sudden rise in tension. As a physics teacher, he knows all about the laws of action and reaction.
"We have always gotten along in Pakistan," he said. "When I got married, Muslim friends came here to this same church. But once this thing starts to spread, who knows how it goes?"
If nothing triggers a violent outbreak, Yaqoob added, the tension might pass.
"I think 75 percent of Pakistanis hate terrorism and are against Usama bin Laden," he said. "Only 20 percent maybe are fundamentalists. It is always the negative which makes the most noise."
But, he added, any confrontation would likely polarize the two religions, with extremists using the occasion to rally support among the poorly educated masses.
For now, there is nothing close to panic, and opinions vary as to potential danger.
Lal Masih, at 70, might have fallen out of a Rudyard Kipling novel, with enormous white mustaches billowing out from under thick round glasses and a colorful skullcap.
Asked if he was worried, he smiled and pointed a forefinger heavenwards.
Harrison John is 13 but looks younger, the son of a church official. He grinned and declared himself unafraid.
But S.M. Shafiq and Faved Hadayet, lab technicians, shared a different view. They heard continual threats. Neither had encountered any problems. But, both said, things might change in an instant.
"If America bombs Afghanistan," Shafiq said, "anything could happen."
Sacred Heart is reached behind a wooden gate with no sign on Jinnah Road in the center of Quetta. About 100 people can fit inside the simple church with a game attempt at vaulted ceilings.
Mass follows classic lines but is decidedly Pakistani. Lively hymns are accompanied by an accordion and bongo drums.
The faithful who line up for communion look no different from their Muslim countrymen. Women in modest headscarves stay to one side. Men wear knee-length loose shirts, baggy pants and sandals.
Father Eric Lakman, a Sri Lankan who is the priest at Sacred Heart, dates Catholicism in the Indian subcontinent back to the 6th century. He says the religion flourished from the time of Saint Matthew.
Under the British Raj, which lasted until 1947, Anglican congregations also grew.
In recent years, Father Eric said, Muslims and Christians have gotten along well in Pakistan. Today, however, he sees something new.
"Oh, definitely," he said, when asked if he felt extremists might attack Christians. "If they attack, we'll be among the first martyrs." With a nervous laugh, he added: "But we will not run anywhere."
The Associated Press contributed to this report.