The New York Times newspaper has published what it says are the findings of a classified US intelligence paper on the effects of the Iraq war.
The violence in Iraq shows little sign of abating
The document reportedly blames the three-year-old conflict for increasing the threat of terrorism and helping fuel Islamic radicalism worldwide.
However, a White House spokesman said the newspaper report was "not representative of the entire document".
The paper has not seen the report, but spoke to people familiar with it.
The BBC's defence correspondent Rob Watson says this is not the first time the US intelligence community has said that the war in Iraq has made the problem of Islamist extremism worse.
Indeed it had warned that might happen even before the US-led invasion in 2003.
But, our correspondent says, this latest finding, known as a National Intelligence Estimate, is the most comprehensive report yet, based on the considered analysis of all 16 of the US intelligence agencies.
Many have been inspired by al-Qaeda chief Osama Bin Laden
According to the New York Times, which has spoken to officials who have either read it, or been involved in drafting it, the report says the invasion and occupation of Iraq has spawned a new generation of Islamic radicalism that has spread across the globe.
It also warns that Islamic militants who have fought in Iraq could foment radicalism and violence when they return to their home countries, much as returning Jihadis did after the war against the Soviet Union in Afghanistan in the 1980s.
It reportedly concludes that, while al-Qaeda may have been weakened since the 11 September 2001 attacks, the radical Islamic movement worldwide has strengthened with the formation of new groups and cells who are inspired by Osama Bin Laden, but not under his direct control.
But White House spokesman Peter Watkins hit back at the newspaper's report, saying: "Their [terrorists'] hatred for freedom and liberty did not develop overnight, those seeds were planted decades ago.
"Instead of waiting while they plot and plan attacks to kill innocent Americans, the United States has taken the initiative to fight back."
However, the report will make uncomfortable reading at the White House, our correspondent says.
In a series of recent speeches, President George W Bush has been portraying the war in Iraq as the central front in the war on terrorism. This report implies while that may be true, that it is a front of America's own making.
In the past, Mr Bush has dismissed such reasoning by arguing that Islamic militants had hated the US long before it invaded Iraq, or even Afghanistan for that matter.