There are less formal pledges of support from “probably at least a couple hundred extremists” in countries such as Jordan, Lebanon, Saudi Arabia, Tunisia, and Yemen, said a US counterterrorism official who spoke on the condition of anonymity to discuss confidential information about the group.

WASHINGTON — The Islamic State is expanding beyond its base in Syria and Iraq to establish militant affiliates in Afghanistan, Algeria, Egypt, and Libya, US intelligence officials assert, raising the prospect of a new global war on terror.

Lieutenant General Vincent R. Stewart, the director of the Defense Intelligence Agency, said in an assessment this month that the Islamic State is assembling a growing international following.


Nicholas Rasmussen, the director of the National Counterterrorism Center, echoed Stewart’s analysis in testimony before Congress last week.

But it is unclear how effective these affiliates are, or to what extent this is an opportunistic rebranding by some jihadist upstarts hoping to draft new members by playing off the notoriety of the Islamic State.

Critics fear such assessments will once again enmesh the United States in a protracted, hydra-headed conflict as President Obama appeals to Congress for new war powers to fight the Islamic State.

“I’m loath to write another blank check justifying the use of American troops just about anywhere,” said Representative Adam B. Schiff of California, the senior Democrat on the House Intelligence Committee.

The sudden proliferation of Islamic State affiliates and loyalist fighters motivated the White House’s push to give Obama and his successor new authority to pursue the group wherever its followers emerge — just as he and President George W. Bush hunted Al Qaeda franchises outside the group’s headquarters, first in Afghanistan and then in Pakistan, for the past decade.


“We don’t want anybody in ISIL to be left with the impression that if they move to some neighboring country, that they will be essentially in a safe haven and not within the range of United States capability,” Josh Earnest, the White House press secretary, said Wednesday, using an acronym to refer to the Islamic State.

The Islamic State began attracting pledges of allegiance from groups and individual fighters after it declared the formation of a caliphate, or religious state, in June. Counterterrorism analysts say it is using Al Qaeda’s franchise structure to expand its geographic reach, but without Al Qaeda’s rigorous, multiyear application process.

This could allow its franchises to grow faster, easier, and farther.

“Factions which were at one time part of Al Qaeda and its affiliates, as well as groups loyal to it or in some ways working in tandem with it, have moved on to what they see as more of a winning group,” said Steven Stalinsky, executive director of the Middle East Media Research Institute in Washington, which monitors Arabic-language media and websites.

There is no indication that the Islamic State controls territory in Afghanistan, but it has signaled its interest in Afghanistan and Pakistan and has reportedly sent envoys there to recruit.

Similarly, until recently, leaders of Al Qaeda in the Arabian Peninsula, in Yemen, used nonconfrontational language to mask simmering disagreements with the Islamic State and its head, Abu Bakr al-Baghdadi. But tensions peaked in November, when a faction of Al Qaeda fighters there swore loyalty to Baghdadi.


Any authorization to use US military force against the Islamic State could arguably also cover interventions in Egypt and Libya, where active militant organizations have pledged allegiance to the group and have received its public acknowledgment as “provinces” of the putative caliphate.

Although there is little or no public evidence that the Islamic State’s leaders in Syria and Iraq have practical control over its North African provinces, its influence is already apparent in their operations and is destabilizing the countries around them.

A publication released by the central group last week included a photograph of fighters in Libya with its affiliate there parading 20 Egyptian Christian captives in the Islamic State’s trademark orange jumpsuits, indicating at least a degree of communication.

In Egypt, the Sinai-based extremist group Ansar Beit Al Maqdis sent emissaries to the Islamic State in Syria last year to seek financial support, weapons, and tactical advice, as well as the publicity and recruiting advantages that might come with the Islamic State name, Western officials briefed on classified intelligence reports said.

In neighboring Libya, at least three distinct groups have declared their affiliation with the Islamic State .