President Obama tried to calm the American public Sunday night following the terrorist attack in San Bernardino, California, and he called on Congress to make it more difficult for would-be terrorists to acquire weapons, particularly military assault rifles like the ones used in San Bernardino.
"I know that after so much war, many Americans are asking whether we are confronted by a cancer that has no immediate cure," the president said.
"The threat from terrorism is real, but we will overcome it," he said.
Obama's rare Oval Office speech comes as Americans have been left shaken by attacks in San Bernardino, California, and in Paris.
Obama called the San Bernardino attack an "act of terrorism designed to kill innocent people," but said there was no evidence that the killers were directed by a terrorist organization overseas or that they were part of a broader network.
"But it is clear that the two of them had gone down the dark path of radicalization," he said.
On Wednesday, Tashfeen Malik and her husband, Syed Rizwan Farook, opened fire at the San Bernardino health department's holiday lunch, killing 14 people and wounding another 21. It was the worst terrorist attack in the United States since Sept. 11, 2001. The couple, whom the Islamic State on Saturday identified as supporters, had collected assault rifles, pipe bombs and thousands of rounds of ammunition.
Last month, 130 people were killed when three teams of attackers carried out an assault on the Bataclan theater and other spots in Paris, while earlier, a Russian airliner was brought down over the Sinai Peninsula. Both are attributed to the Islamic State.
Obama said that since the Sept. 11, 2001, attacks the United States had hardened its defenses, killed Osama bin Laden and disrupted countless plots. But over the last few years, the terrorist threat has evolved and terrorists have turned to less complicated acts of mass violence, he said, and cited the San Bernardino attack and others.
Obama spelled out how the United States was battling the Islamic State -- by training forces in Iraq and Syria, working with allies to cut off its funding, relying on special operations and airstrikes and negotiating a cease fire to the Syrian civil war so that the focus could be on a common enemy.
He called on Congress to ensure that no one on "no fly" lists should be allowed to buy a gun, a step Congress has rejected, and to make it more difficult for people to buy assault weapons.
"What we can do, and must do, is make it harder for them to kill," he said.
Republicans have remained adamantly opposed to any new gun restrictions.
Obama also said that Congress should pass authorization for military actions underway in Iraq and Syria. He said that there must be stronger screening for those who come to the United States without a visa and said he had ordered the departments of State and Homeland Security to review the visa waiver program.
But he said the country could not be drawn into another long and costly ground war that would lure new recruits to organizations like the Islamic State.
"The strategy that we are using now, airstrikes, special forces and working with local forces who are fighting to regain control of their own country, that is how we will achieve a more sustainable victory," he said.
And he said the country could not turn the war against organizations like the Islamic State, or ISIL, which he described as made up of thugs and killers who are part of a "cult of death," into a war against Islam.
"We cannot turn against one another," he said.
To succeed in defeating terrorism, the United States must enlist Muslim communities as some of its strongest allies, Obama said.
"That does not mean denying the fact that an extremist ideology has spread within some Muslim communities," he said. "That's a real problem that Muslims must confront without excuse."
All Americans of all faiths must reject discrimination, he said. If the United States starts treating Muslims differently, it will betray its values and play into the hands of extremists, he said.
"Freedom is more powerful than fear," he said.
Republican presidential hopefuls have routinely criticized Obama's policies against terrorism as ineffective and dangerous for the country.
Before the speech, on "Meet the Press," Republican candidate Sen. Lindsay Graham said he wanted to hear that Obama would back a regional army to destroy the Islamic State in its base in Raqqa, Syria.