Media playback is unsupported on your device Media caption Obama said he hoped the pastor would call off the 'stunt' - Pictures courtesy Good Morning America

US President Barack Obama says plans by a small church to burn copies of the Koran on the anniversary of 9/11 are a "recruitment bonanza" for al-Qaeda.

Mr Obama said if the burning went ahead in Gainesville, Florida, it could endanger US military personnel serving in Pakistan and Afghanistan.

The plan has drawn widespread international condemnation.

Interpol has issued a global alert, warning the burning could provoke "violent attacks on innocent people".

The US State Department has advised American citizens abroad to be on the alert for possible attacks and to avoid areas where demonstrations might take place.

Terry Jones, the pastor behind the threat, leads a small congregation in the city of Gainesville.

He has said the burning would be a way to stand up to terrorism.

In an interview with ABC television, Mr Obama said he hoped Mr Jones "understands that what he's proposing to do is completely contrary to our values as Americans, that this country has been built on the notion of freedom and religious tolerance".

It will inflame sentiments among Muslims throughout the world and cause irreparable damage to interfaith harmony Asif Ali Zardari , Pakistan president

"And as a very practical matter, I just want him to understand that this stunt that he is talking about pulling could greatly endanger our young men and women who are in uniform," the president said.

"Look, this is a recruitment bonanza for al-Qaeda. You could have serious violence in places like Pakistan and Afghanistan. This could increase the recruitment of individuals who'd be willing to blow themselves up in American cities, or European cities," he said.

"I hope he listens to those better angels and understands that this is a destructive act that he's engaging in," the president said.

Later on Thursday, US officials said they were considering contacting Mr Jones directly to urge him to reconsider his plans.

Mr Jones had told USA Today he could potentially cancel his plans if officials spoke to him directly.

Defence Secretary Robert Gates was considering "taking this unusual measure of calling this pastor and trying to convince him that it is not the right thing to proceed with," said Pentagon press secretary Geoff Morrell.

'Diseased mind'

Mr Jones said on Wednesday that his plan to burn the Islamic holy book was intended to draw attention to his belief that "something's wrong".

Analysis Burning a religion's holy book is an unmistakably offensive act, but in America, it is also a protected one. The First Amendment to the US Constitution enshrines the right to freedom of speech. It is therefore illegal for a government to ban forms of speaking. The United States Supreme Court has ruled on several occasions that free speech includes symbolic actions. That is why it is perfectly legal for protesters to burn the American flag or for the Ku Klux Klan to burn crosses, even though such actions outrage and offend. Threatening messages which directly incite violence or lawless behaviour are exceptions. In those cases, the advocate can be arrested. Pastor Terry Jones has said that he is just making a point with his Koran bonfire - he is not advocating physical harm of Muslims, so his actions are constitutionally protected. The only legal avenue open to to the Florida authorities is to fine Pastor Jones for burning outdoors without a permit. Right now, he does not have one. Mark Mardell: A moment of agreement Viewpoint: No great trick to burn a book Koran burning threat: Your reaction

"It is possibly time for us in a new way to actually stand up, confront terrorism," Mr Jones told reporters outside his church.

US officials say they cannot intervene as the church's actions would probably be protected by the US constitution's guarantee of freedom of speech.

Interpol, the international police organisation, has issued an alert to all of its 188 member states, warning of "a significant threat to public safety".

"If the proposed Koran burning by a pastor in the US goes ahead as planned, there is a strong likelihood that violent attacks on innocent people would follow," it said.

The agency said it was acting partly in response to a request from the Pakistani Interior Minister, Rehman Malik.

Earlier, Pakistan's President Asif Ali Zardari said in a statement that "anyone who even thought of such a despicable act must be suffering from a diseased mind and a sickly soul".

"It will inflame sentiments among Muslims throughout the world and cause irreparable damage to interfaith harmony and also to world peace," he said.

Mr Zardari joined leaders of both Muslim and non-Muslim countries in condemning Mr Jones' plans.

Malaysia's Foreign Minister Anifah Aman said it was "a heinous crime" that would "anger the Muslims in Malaysia and throughout the world"

Indonesia said the burning would damage relations between Islam and the West

The UK government said it opposed "any attempt to offend any member of any religious or ethnic group"

US Secretary of State Hillary Clinton called the burning "disgraceful"

The Organisation of the Islamic Conference (OIC), which represents more than 50 states and promotes Muslim solidarity, said Mr Jones was following an "outrageous path of hatred"

On Monday Gen David Petraeus, the top US commander in Afghanistan, warned troops' lives would be in danger if the church went ahead with its bonfire

Image caption Dozens of Muslim schoolgirls take part in a protest at a madrassa (religious school) in Jammu in Indian-administered Kashmir. The Indian government urges the United States to take strong action against Terry Jones. In pictures: Koran burning protests

The website of Mr Jones' church was no longer accessible on Thursday, after the company hosting it withdrew it from the internet for "violating the Offensive Content section of its Acceptable Use policy".

Rackspace told the BBC it was "a stout supporter of freedom of speech" but that it asserted the right "as a private company to promote an environment of civility within its business".

Muslims consider the Koran to be the word of God and insist it be treated with the utmost respect. Any intentional damage or show of disrespect to the holy book is deeply offensive to them.