FBI agents visited Thursday with a minister of a small Florida church that plans to burn the Quran on Sept. 11, as public safety became a paramount concern and President Barack Obama added his voice to the chorus of opposition.
Elsewhere, hundreds of angry Afghans burned an American flag and chanted "Death to the Christians" to protest the planned burning of Islam's holiest text.
Mr. Obama urged the Rev. Terry Jones toand call off his plan.
In an interview with ABC's "Good Morning America," Mr. Obama said what Jones proposes "is completely contrary to our values as Americans. This country has been built on the notion of freedom and religious tolerance."
Meanwhile, the State Department issued a travel alert "to caution U.S. citizens of the potential for anti-U.S. demonstrations in many countries" in response to the planned burning of Qurans.
The FBI spent about a half hour talking with Jones, but church spokesman Wayne Sapp would not disclose what they discussed. Agents leaving the church wouldn't talk to an Associated Press reporter.
Last month Jones said in a deposition that he met with the FBI regarding threats to his life and property.
Jones will make a statement later Thursday that will address the FBI visit and the president's statement imploring him to cancel the burning and calling it a "stunt," his spokesman said.
There was one small sign the pastor who's never read the Quran or visited a mosque was willing to hear from the other side, CBS News Correspondent Kelly Cobiella reports. Jones spent 30 minutes with a local imam.
"I think the pastor as a Christian will follow in the footsteps of Christ and will do the right thing," Imam Muhammad Musri told CBS News.
Jones' own daughter has told a Gainesville newspaper that his church is a cult, closed to the outside world and controlled by Jones, who in depositions for a lawsuit said Hinduism, Buddhism and Judaism all are "of the devil," Cobiella reports.
Florida Gov. Charlie Crist said he would closely monitor what happens Saturday at the Dove Outreach Center in Gainesville to try to ensure people are safe. U.S. embassies around the world will be doing the same after being ordered by the State Department to assess their security. Officials fear the burning could spark anti-American violence, including against soldiers.
"In addition to being offensive, the Gainesville protest puts at risk those brave Americans who are fighting abroad for the freedoms and values that we believe in as Americans," said Crist, who is running as an independent for the U.S. Senate.
On CBS' "The Early Show" Thursday, Minnesota Congressman Keith Ellison - the first Muslim ever elected to Congress - echoed Mr. Obama's feelings, but called for restraint in response.
"I think it certainly has the potential to hurt Americans in uniforms of our country. I think it also damages our Constitution. It damages the fabric of our nation that is based on the idea of religious liberty," Ellison said. "But the thing I'd like to say is that I urge people in congregations, Muslim and other, to urge restraint, to urge patience and to urge caution. You should not reward this provocation with a counter-response."
"I would ask religious leaders to speak to their congregations and say, he's trying to provoke you. Don't be provoked," he said.
The international police organization Interpol issued a global alert to its 188 member-countries determining "strong likelihood" of violent attacks if the burn goes forward. Interpol said in a statement that Pakistan's interior minister, Rehman Malik, called the organization and asked it to warn other police forces around the world of an increased terror threat.
Despite the mounting pressure to call off the bonfire, Jones said he has received much encouragement and supporters have sent him copies of the Quran to burn.
"As of right now, we are not convinced that backing down is the right thing," said Jones, 58, who took no questions at a news conference Wednesday.
Jones said in an interview with USA Today that he had not been contacted by the White House, State Department or Pentagon. If such a call comes, he said, "that would cause us to definitely think it over. That's what we're doing now. I don't think a call from them is something we would ignore."
At Wednesday's news conference, Jones was flanked by an armed escort and said he has received more than 100 death threats since announcing in July that he would stage "International Burn-a-Koran Day." The book, according to Jones, is evil because it espouses something other than biblical truth and incites radical, violent behavior among Muslims.
Muslims consider the Quran the word of God and insist it be treated with the utmost respect. At least one cleric in Afghanistan said it is the duty of Muslims to react and that could mean killing Americans.
In Gainesville, police will already be dealing with some 90,000 football fans Saturday and even more tailgaters for the Florida-South Florida game.
Gainesville Mayor Craig Lowe condemned the church's plans and asked residents to watch for suspicious behavior. At least one counter-protest was planned by a University of Florida student group.
City officials were increasing security, but wouldn't go into detail about how many extra officers will be used, saying only that they were coordinating with other cities and tallying expenses.
"We are sending a bill for services to the Dove World Outreach Center. We're tracking our costs," said city spokesman Bob Woods. "I'm sure the cost will be substantial."
Gen. David Petraeus, the top U.S. and NATO commander in Afghanistan, e-mailed The Associated Press to say "images of the burning of a Quran would undoubtedly be used by extremists in Afghanistan - and around the world - to inflame public opinion and incite violence." It comes as an emotional debate continues over a proposed Islamic center near the ground zero site of the 2001 terrorist attacks in New York.
Pentagon Spokesman Jeff Morell said Wednesday that there were discussions to determine if someone from the government should call the pastor. He said Gates was part of the discussions. Another source tells CBS News that the call would come from either the White House, State Department or the Pentagon.
Secretary of State Hillary Rodham Clinton said that the pastor's plans were outrageous, and along with Defense Secretary Robert Gates, urged Jones to cancel the event.
Not just the Democratic administration has weighed in. Ex-Alaska governor and former Republican candidate for vice presidentthat although people have the constitutional right to burn the Quran, doing so would be an "insensitive and an unnecessary provocation - much like building a mosque at ground zero."
Conservative radio and television host Glenn Beck wrote in an Internet blog that burning the Quran is like burning the flag or the Bible - something people can do in the United States, but shouldn't. Legal experts have said the burning would likely be protected by the First Amendment's right to free speech.
The foreign ministries of Pakistan and the Gulf nation of Bahrain issued some of the first official denunciations in the Muslim world, with Bahrain calling it a "shameful act which is incompatible with the principles of tolerance and coexistence." Bahrain is home to the U.S. Fifth Fleet, which is responsible for naval forces in the Persian Gulf.
The president of Indonesia, the world's most populous Muslim nation, has also sent a letter to Obama asking him to stop the bonfire.
In Pakistan, about 200 lawyers and civil society members marched and burned a U.S. flag in the central Pakistani city of Multan, demanding that Washington halt the burning of the Muslim holy book.
"If Quran is burned, it would be beginning of destruction of America," read one English-language banner held up by the protesters, who chanted "Down with America!"
Jones' Dove Outreach Center is independent of any denomination. It follows the Pentecostal tradition, which teaches that the Holy Spirit can manifest itself in the modern day. Pentecostals often view themselves as engaged in spiritual warfare against satanic forces.
The Vatican also denounced the protest and a religious watchdog group, Military Religious Freedom Foundation, said it would send a copy of the Quran to the Afghan National Army for every one that might be burned.
Franklin Graham, the son of evangelist Billy Graham, tried to call Jones twice on Wednesday but was unable to reach him and has now written him a letter urging him not to proceed, according to a spokesman.
"It's never right to deface or destroy sacred texts or writings of other religions even if you don't agree with them," Franklin Graham said in a statement.
In 2001, Graham described Islam as evil. The U.S. Army earlier this year rescinded his invitation to speak at a Pentagon prayer breakfast after a religious freedom group raised an objection, citing his past remarks.