The head of the CIA offered a dire outlook on the prospect of the United States rooting out the Islamic State in Iraq and Syria (ISIS), saying Thursday the terror group aims to extend its reach and is undaunted in carrying out attacks.

{mosads}But ISIS’s ability to launch attacks remains as firm as ever, Brennan said, and its areas of control outside its self-proclaimed caliphate continue to grow.

While military efforts against ISIS in Syria are proceeding, they have been hindered by the long civil war between rebels and President Bashar Assad, who is being aided by Russia, Brennan said. Assad’s grip on power is stronger than it was a year ago, the CIA chief added.

ISIS “is a formidable, resilient and largely cohesive army, and we anticipate that the group will adjust its strategy and tactics in an effort to regain momentum,” Brennan said at a rare public hearing of the Senate Intelligence Committee.

“This is a global challenge. The number of ISIL fighters now far exceeds what al Qaeda had at its height. We’re talking about tens of thousands of individuals,” he said, using an alternate acronym for the terror group. 

That reach, Brennan said, is growing as ISIS tries to “increase its influence in Africa and to plot attacks in the region and in Europe.”

In particular, the CIA head warned of the growing strength of ISIS affiliates outside of Iraq and Syria, including branches in Libya and Egypt. Nigeria’s Boko Haram has also pledged allegiance to ISIS and is considered to be the deadliest terror group in the world.

In Libya, ISIS has seized control of a sizable portion of the Mediterranean coast, which Brennan feared could be used to launch attacks into Europe. 

“That is very concerning, particularly since Libya is right across from Europe, over the Mediterranean, and refugee flows are going there,” he said. Refugee routes are one of several avenues ISIS fighters might be exploring to sneak into Western countries and launch attacks, Brennan added.

There are between 5,000 and 8,000 ISIS fighters in Libya, Brennan said, more than double last year’s estimates. In the same time, the number of fighters in Syria and Iraq has dropped from roughly 33,000 to somewhere between 18,000 and 22,000.

Another approximately 1,000 “hardcore fighters” are in Egypt’s Sinai Peninsula, as well as hundreds more in Yemen, Afghanistan and Pakistan, he said. There are roughly 7,000 extremist fighters in Nigeria.

“The numbers are significant,” Brennan told the Intelligence Committee.

Brennan’s description is likely to deal a blow to supporters of the Obama administration’s efforts against ISIS. The administration has been largely stymied in its effort to calm the chaos created by the Syrian civil war and the broader rise of global terrorism. 

The Pentagon has been ridiculed over the meager results of its efforts to train Syrian rebels, which yielded just a handful of recruits despite hundreds of millions of dollars spent.

Military gains have been successful reducing the group’s grip on power in its center, Brennan said.

But to compensate, ISIS “will probably rely more on guerrilla tactics, including high-profile attacks outside territory it holds,” Brennan predicted.

“Unfortunately, despite all our progress against ISIL on the battlefield and in the financial realm, our efforts have not reduced the group’s terrorism capability and global reach,” he said. “The resources needed for terrorism are very modest and the group would have to suffer even heavier losses of territory, manpower and money for its terrorist capacity to decline significantly.”

The turmoil in Syria has allowed ISIS to continue to actively plan and train operatives to launch attacks in foreign countries. Part of that, Brennan indicated, is due to reluctance from Russia to encourage Assad to step aside and bring calm to the country.

“A year ago, he was on his back foot as the opposition forces were carrying out operations that really were degrading the Syrian military,” Brennan said. “As result of the Russian military intervention, he is in a stronger position than he was in June of last year.”