|Protests against the Quran buring have already been held in Pakistan and Indonesia [AFP]
Barack Obama, the US president, has warned that the number of people willing to fight for al-Qaeda will increase if a burning of the Quran is carried out as planned by a US church group.
"This could increase the recruitment of individuals who'd be willing to blow themselves up in American cities, or European cities," Obama said in an ABC television interview on Thursday, calling the burning a stunt.
"You know, you could have serious violence in places like Pakistan or Afghanistan ... This is a recruitment bonanza for Al-Qaeda," he said.
The Obama administration said that it was deciding whether to make a direct appeal to the church group to call off the plan.
Meanwhile, Craig Lowe, the mayor of Gainesville, where the burning is to take place, has said that there is a "plan in place" to deal with the event which is "being modified" as new information is received. Lowe did not give further details.
Interpol, the international police agency, also warned that there will be an increased risk of attacks worldwide if the if the burning occurrs.
"If the proposed Quran burning by a pastor in the US goes ahead as planned, there is a strong likelihood that violent attacks on innocent people would follow," Ronald Noble, Interpol's secretary general, said on Thursday.
Interpol also said that it was acting partly on a request from Pakistan.
Ban Ki-moon, the UN secretary general, stepped up his condemnation of the "unacceptable" plan.
Ban said all countries must have more respect for other religions.
"I sincerely hope that they will not take such unacceptable actions," Ban said.
The leader of the small church in the US state of Florida planning to hold the burning said on Wednesday that he is determined to go through with the plan, despite an international outcry against it.
Terry Jones, the pastor, said that he has received encouragement for his protest, with supporters mailing copies of the Islamic holy text to his church in Gainesville.
The plan is to incinerate the Qurans in a bonfire on Saturday to mark the ninth anniversary of the September 11, 2001 attacks on New York and Washington.
"As of right now, we are not convinced that backing down is the right thing," Jones said.
'Outrageous and grave'
Jones said he has received more than 100 death threats and has started wearing a gun since announcing his plan to burn the book that Muslims consider the word of God.
However, reports have said that Jones has accepted the support of Right Wing Extreme, said to be an armed Christian organisation, to protect the church with between 500 and 2,000 men.
The 58-year-old pastor proclaimed in July that he would stage 'International Burn-a-Quran Day.'
The plan has already sparked protests in Afghanistan and Indonesia and US officials are worried that it will put Americans at risk.
General David Petraeus, the US and Nato commander in the Afghan capital, Kabul, warned that "images of the burning of a Quran would undoubtedly be used by the Taliban in Afghanistan, to inflame public opinion and incite violence".
The Vatican also denounced the planned Quran burning as "outrageous and grave".
Jones' actions likely would be protected by the US constitution's right to free speech.
The US Supreme Court has made clear that speech deemed offensive to many people, even the majority of people, cannot be suppressed by the government unless it is clearly directed to intimidate someone or amounts to an incitement to violence, legal experts have said.
The website of the Dove World Outreach Centre was shut down on Thursday by its web hosting company.
Rockspace said that the church group has violated its "acceptable use policy", being a contract rather than consitutional issue.
Some of Al Jazeera's servers are also hosted with Rockspace.
Gainsville elected the openly-gay Lowe as mayor earlier this year.