Obama authorizes U.S. military strikes against Islamic State leaders, officials say

The scope of the United States counterterrorism fight is poised to expand again as U.S. military officials said yesterday that they were given new authority to begin targeting leaders of an al-Qaida rival known as the Islamic State.

A day after President Barack Obama vowed to "degrade and ultimately destroy" the extremist group, U.S. intelligence officials said the CIA has completed a new assessment of the Islamic State's strengths, showing that it has more than doubled in size in recent months.

"CIA assesses the Islamic State of Iraq and the Levant (ISIL) can muster between 20,000 and 31,500 fighters across Iraq and Syria, based on a new review of all-source intelligence reports from May to August, an increase from our previous assessment of at least 10,000 fighters," according to a CIA spokesman, using another name for the group, which he discussed on the condition of anonymity. "This new total reflects an increase in members because of stronger recruitment since June following battlefield successes and the declaration of a caliphate, greater battlefield activity, and additional intelligence."

At the same time, details of how the Pentagon will pursue the new offensive began to emerge. U.S. military officials said they have new authority to carry out strikes against the group's leaders, including Abu Bakr al-Baghdadi, who earlier this year declared himself the head of a restored caliphate.

Such targets had been off-limits under the more narrow terms of an air campaign that Obama had described as a humanitarian effort to protect members of religious minorities and also shield American diplomats from Islamic State fighters in Iraq.

Pentagon officials described their altered mission as a shift to offense from defense. "We're going to intensify our efforts inside Iraq, there's no question about that," said Adm. John Kirby, the Pentagon press secretary.

In remarks to reporters, Kirby declined to answer directly when asked whether the Pentagon now had a green light to hunt down individuals, but he said: "One of the ways you get at, and you destroy the capabilities of an enemy like ISIL is to be pretty aggressive against them. And that does include disrupting their ability to command and control, and to lead their own forces."

Kirby said the 475 additional U.S. troops that Obama ordered to Iraq will arrive over "the next week or so." Among them are a detachment of about 125 personnel who will operate armed U.S. surveillance aircraft for the first time from Irbil, the capital of the Kurdish region.

Kirby said officials are still considering which types of aircraft to send to Irbil but that the fleet will not include drones.