The United Nations Secretary General Ban Ki-moon has added his voice to appeals to a fringe evangelical church in Florida not to go ahead with plans to burn copies of the Koran.
The event is scheduled to take on Saturday to mark the ninth anniversary of the 11 September terrorist attacks.
There has been widespread condemnation from political and religious leaders of the burning.
The organiser, Pastor Terry Jones of the Dove World Outreach Center, said his church was not backing down.
US Secretary of State Hillary Clinton has condemned the pastor's plans, labelling them 'disrespectful' and 'disgraceful'.
Speaking at the State Department, Mrs Clinton said she was heartened by the clear, unequivocal condemnation that had come from religious leaders of all faiths.
'Our commitment to religious tolerance goes back to the very beginning of our nation,' she added as she hosted an iftar meal at the State Department to celebrate the Muslim holy month of Ramadan.
Her comments made her the highest-ranking US official to express concern over the incendiary move by a group of US evangelicals that military leaders warn could trigger outrage around the Islamic world and endanger the lives of US soldiers.
Mrs Clinton's spokesman Philip Crowley earlier denounced Florida Pastor Jones's plans to mark Saturday's ninth anniversary of the 11 September attacks by burning Korans as 'provocative' and 'un-American'.
'We would like to see more Americans stand up and say that this is inconsistent with our American values,' he added.
'The potential act of burning a Koran... is contrary to our values, contrary to how civil society has emerged in the country.'
The small Florida church's planned open-air burning ceremony triggered a wave of concern and condemnation from military leaders.
But Pastor Jones said the proposed event would send a clear message to the radical element of Islam.
The US commander of foreign forces in Afghanistan, General David Petraeus, said that the evangelists would be putting US troops in danger if they went ahead with their demonstration.
There are more than 100,000 US troops in Afghanistan.
'We are taking his concerns very seriously,' Pastor Jones told CNN, referring to General Petraeus, but 'we right now have plans to continue.'
Although the fire authorities turned down an application a few weeks ago from Mr Jones to hold the open-air burning ceremony, police cannot intervene until they actually light the 200 Korans.
Even then, no arrests would be made as contravening local ordinances is only a misdemeanour, and citations - fines and warnings - are issued in such cases.
Mr Jones said the Koran torching aimed 'to remember those who were brutally murdered on September 11', and to send a warning 'to the radical element of Islam'.
Saturday's anniversary is set to coincide with festivities for Eid al-Fitr, which marks the end of the holy month of Ramadan, a time of prayer and fasting for nearly 1.5bn Muslims worldwide.
Mr Jones remained defiant. 'Instead of us being blamed for what other people will do or might do, why don't we send a warning to them?' he said.
Religious bigotry was roundly condemned at a press conference called by the coalition of inter-faith leaders.
'To those who would exercise derision... bigotry, open rejection of our fellow Americans for their religious faith, I say shame on you,' said Richard Cizik, one of the country's most prominent evangelical leaders.
'We are profoundly distressed and deeply saddened by the incidents of violence committed against Muslims in our communities. And by the desecration of Islamic houses of worship,' added Rabbi Nancy Kreimer.
There have already been protests in the Afghan capital Kabul and in Indonesia - the world's largest Muslim-majority country - against Mr Jones's plans, while Iran has warned it could unleash an uncontrolled Muslim response.