Washington: The speed at which the Islamic State, America's latest Islamist adversary, has grown, amassed resources and recruited Western fighters have prompted US to respond differently than it did to terror groups elsewhere, a senior Obama administration official has said.
"At least at this stage, it's a really different type of threat that it poses," Lisa Monaco, assistant to the US president for homeland security and counter-terrorism, said.
The White House considered that targeting the Islamic State (IS) directly could intensify its motivation to strike the United States, Monaco said, which is part of why President Barack Obama and others have made a point of questioning the extremist group's religious credentials and overall legitimacy.
But she noted that the group has already made clear its intent to target the country.
"We conduct that analysis, but they've already shown their brutality," she was quoted as saying by Washington Post.
However, the report noted that US intelligence agencies remain uncertain about danger posed by IS.
It recalled that hours before Obama announced a new US military offensive against the IS, one of his top counter? terrorism officials testified to Congress that the al-Qaeda offshoot had an estimated 10,000 fighters.
The next day, the CIA came out with a new assessment, saying the terrorist organisation's ranks had more than doubled in recent months, surging to somewhere between 20,000 and 31,500 fighters across Iraq and Syria.
"The enormous discrepancy reflects, in part, significant uncertainty among U.S. Intelligence agencies over the dimensions of and danger posed by America's latest Islamist adversary," the report said.
But the trajectory of those numbers and the anxiety that they have induced among US counter-terrorism and military officials also helps to explain Obama's decision to go to war against an Islamist group that has yet to be linked to any plot against the United States.
In his speech, Obama laid out a rationale that leaned heavily on what-ifs. The United States has "not yet detected specific plotting against our homeland," Obama said. But Islamic State leaders "have threatened America and our allies," he said, and are on a path to deliver on those threats "if left unchecked."
"The emphasis on hypotheticals was notable for a commander-in-chief who presided over the creation of a counter-terrorism doctrine in which US strikes are supposed to be contemplated only in cases of imminent threat of violent attack. Faced with a terrorist group that is expanding faster than US spy agencies can chart it, the "imminent" threshold appears to have been set aside, the report noted.
When asked about the revised estimates of Islamic State
fighters on Friday, White House press secretary Josh Earnest said it indicates "that the group has had some recruitment success after the battlefield advances that they demonstrated back in June, and it reflects some better insight that the intelligence community has been able to gain into the activities" of the IS.
Several factors have fed US anxiety, the report said, citing the IS's seizure of large chunks of territory in Iraq and Syria has been particularly unnerving to US officials and agencies still haunted by the extent to which a haven in Afghanistan served as an incubator for al-Qaeda and the September 11, 2001, attacks.
US officials have also cited the danger posed by the massive flow of foreign fighters into Syria ? including at least 2,000 holding Western passports, enabling them to emerge from the Syrian civil war with Islamist contacts, lethal training and the potential ability to travel throughout Europe and North America unimpeded.
Senator Dianne Feinstein, the chairman of the Senate Intelligence Committee, wrote in a recent op-ed that "the threat ISIS poses cannot be overstated."
She went on to describe the IS as "the most vicious, well-funded and militant terrorist organisation we have ever seen."
Although aspects of Feinstein's characterisations are accurate, confusion about the group stems to a large degree from the difficulty in extrapolating its danger to the United States from such adjectives, the report said.
The Islamic State emerged from the remnants of an al- Qaeda affiliate in Iraq that was largely dismantled before US forces left the war-torn country in 2011. But the group has taken advantage of the chaos in Syria's civil war and sectarian tensions in Iraq to regroup.