Oren Dorell

USA TODAY

WASHINGTON — The Islamic State militant group will "almost certainly" remain a threat to the U.S. homeland and seek to launch or inspire attacks on American soil in 2016, a top U.S. intelligence official warned Tuesday.

Attacks in the United States by the group, also known as ISIL, "will probably continue to involve those who draw inspiration from the group's highly sophisticated media without direct guidance from ISIL leadership," James Clapper, director of national intelligence, testified in a rare public hearing on Capitol Hill about intelligence threats facing the nation.

Testifying with Clapper were the director of the Defense Intelligence Agency, Marine Lt. Gen. Vincent Stewart; CIA Director John Brennan; FBI Director James Comey; and Navy Adm. Michael Rogers, who heads the National Security Agency.

Clapper called the Islamic State the "pre-eminent terrorist threat." It can "direct and inspire attacks against a wide range of targets around the world." In a world where violent extremists are active in 40 countries, "ISIL is using the collapse of government authority to expand," he said.

The July attack against military facilities in Chattanooga, Tenn., and the San Bernardino, Calif., terror attack in December "demonstrate the threat that homegrown violent extremists also pose to the homeland," he said.

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Stewart said the Islamic State will probably conduct additional attacks in Europe and then attempt the same in the U.S. He said U.S. intelligence agencies believe ISIL leaders will be "increasingly involved in directing attacks rather than just encouraging lone attackers," according to the Associated Press.

The leaders also listed other threats facing the nation.

Al-Qaeda, which spawned the Islamic State, remains an enemy. The United States will face disparate threats from conflicts spurred by fights over scarce resources caused by climate change and global warming, and drug traffickers selling lethal heroin produced largely in China.

In addition, the nation's cyber infrastructure remains vulnerable to attack by terrorists such as ISIL, as well as by states such as Russia, China, Iran and North Korea, Clapper said.

North Korea has expanded a uranium enrichment facility and restarted a plutonium reactor that could begin recovering material for nuclear weapons in weeks or months, Clapper said.

Clapper said Pyongyang is committed to developing a long-range, nuclear-armed missile capable of posing a direct threat to the United States, "although the system has not been flight-tested."

The nuclear deal reached last summer between world powers and Iran, known as the JCPOA, is likely to limit Iran's nuclear program as intended, but those benefits could be temporary, Clapper said.

"Iran will probably use the JCPOA to remove sanctions while preserving some of its nuclear capability, as well as the option to eventually expand its nuclear infrastructure," he said. "We do not know whether Iran will eventually decide to build nuclear weapons."

Meanwhile, Iran's Islamic Revolutionary Guards, which is conducting military operations against U.S.-supported forces in Syria and Yemen, have not changed its behavior since the deal was signed, and Iran's ballistic missile launches in October and November are "a message they intend to continue to develop their missile program," he said.

In general, the United States is facing a more violent world with a greater variety of threats than it has in 50 years, Clapper said.

"From the Middle East to South Asia, there are probably more cross border conflicts than since the early 1970s," he said.

On the cyber threat, Clapper said U.S. information systems controlled by the U.S. government and American industry are vulnerable to cyberattacks from Russia and China.

Russia, the world's greatest nuclear power along with the United States, has also re-emerged as a possible adversary, Clapper said.

He said Moscow's incursion in Ukraine and other "aggressive" moves around the globe are being taken in part to demonstrate that it is a superpower equal to the United States. He said he's unsure of Russia's end game but is concerned "we could be into another Cold War like-spiral."