Despite suffering major losses in Iraq and Syria, the Islamic State group can still conduct and inspire attacks across the globe, America's spy chief warned senior lawmakers Thursday.
John Brennan, the director of the CIA, testified before the US Senate Intelligence Committee amid renewed fears about IS and the threat of terror attacks, after a gunman slaughtered 49 people in a Florida gay nightclub.
Though the CIA has not found a direct tie between the shooter, Omar Mateen, and any foreign organization, he pledged allegiance to the jihadists and other groups as he perpetrated the worst mass shooting in US history early Sunday.
The IS group has lost much of the territory it once held across its so-called "caliphate" in northern Syria and Iraq, and has seen its ranks thinned by US-led air strikes and desertions.
Authorities estimate between 18,000 and 22,000 IS jihadists remain in Iraq and Syria, down from about 33,000 last year.
But despite upbeat Pentagon assessments about progress in the anti-IS fight, Brennan warned the group is still able to inspire and direct attacks beyond the territory it holds.
IS claimed responsibility for the Orlando massacre and is thought to be behind a string of deadly suicide bombings in Baghdad and Damascus, as well as recent attacks in Paris and Brussels.
"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," Brennan told lawmakers, using an acronym for the IS group.
IS fighters are "probably" exploring a variety of means for sneaking operatives into the West, he added, including in refugee flows, smuggling routes and through regular travel.
"We judge that ISIL is training and attempting to deploy operatives for further attacks," Brennan said.
"ISIL has a large cadre of Western fighters who could potentially serve as operatives for attacks in the West."
Strikes against IS cash hoards and oil smuggling infrastructure have affected the jihadists' financing, but they have made up for the shortfalls through new taxes in the territories it controls and continued smuggling.
And even though it has lost large bands of territory in Syria and Iraq, including major cities like Ramadi, IS is pushing to expand footholds in other countries.
Between 5,000 and 8,000 IS members are based in Libya and another 7,000 in Nigeria, plus hundreds more in Yemen and Afghanistan, authorities estimate.
"The branch in Libya is probably the most developed and the most dangerous," Brennan said.
"It is trying to increase its influence in Africa and to plot attacks in the region and in Europe."
Lawmakers voiced concern about extremists' online outreach and the ease with which they can inspire potential "lone wolf" attackers through the Internet.
Authorities are also troubled about the growing use of encrypted devices and apps that make it difficult for intelligence agencies to monitor communications.
US tech giants and the law enforcement community have been feuding for months about whether the government should have access -- sometimes called a "back door" -- to encrypted communications.
The issue gained new traction after a legal standoff between the FBI and Apple when it refused to unlock an iPhone used by one of the shooters in a mass killing in San Bernardino, California, last year.
Brennan had publicly supported the FBI in the case but he told lawmakers he also supported encryption as a "capability that protects our way of life, our prosperity, our national security."
Still, experts should find a solution "that is not going to be perceived as a back door, but is going to allow the government to legitimately carry out its responsibilities while not compromising the great benefits that accrue to encryption."
Brennan added it was time for the private sector and the government to reach an understanding about "what our respective roles and responsibilities are going to be."