Updated 8:42 a.m., Dec. 7, 2015

WASHINGTON (CBSNewYork/AP) — In a rare Oval Office address, President Barack Obama on Sunday night urged Americans to not give into fear following attacks in Paris and California, while trying to assure the public that he takes the threat of terrorism seriously.

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President Obama vowed that the United States would overcome a terror threat that has entered a “new phase” as he sought to reassure Americans shaken by recent attacks in Paris and California.

“I know that after so much war, many Americans are asking whether we are confronted by a cancer that has no immediate cure,” he said, speaking from a lectern in his West Wing office.

As CBS2’s Valerie Castro reported, President Obama pledged to destroy ISIS.

“Our military will continue to hunt down terrorist plotters in any country where it is necessary. In Iraq and Syria air strikes are taking out ISIL leaders.

Obama called for Congress to continue to authorize airstrikes, but in a just released CNN/ORC poll the majority of Americans, 53 percent, said the U.S. should send ground troops to Iraq and Syria to fight ISIS.

Obama said it’s clear the two killers in the California shootings had gone down the “dark path of radicalization.” He called it an “act of terrorism designed to kill innocent people.”

Obama said the killers had stockpiled weapons and ammunition, but that there’s no evidence the killers were directed by a terrorist organization overseas. He says there’s also no evidence they were part of a broader network in the U.S.

His speech came amid criticism that he has underestimated the threat from an extremist group that claimed responsibility for last month’s deadly attacks in Paris.

Obama also said the U.S. can and must make it harder for would-be mass shooters to kill by making it harder for them to obtain guns.

The President said he knows some people reject all gun safety measures. But he said no matter how effective law enforcement and intelligence is, they can’t identify every would-be shooter. Obama said it’s a matter of national security to prevent those people from getting guns.

“Congress should act to make sure that no one on a no-fly list is able to buy a gun. What could possibly be the argument for allowing a terror suspect to buy a semi-automatic weapon?” the President said.

Obama and other officials urged stricter gun laws following the California shootings, but like previous mass shootings, those calls have met resistance from gun control opponents.

“Two-thousand people on the terrorist watch list successfully bought guns here in America,” Senator Chuck Schumer (D-New York) said.

Gun rights advocates oppose the no-fly list proposal because they say it violates the rights of people who haven’t been convicted of a crime.

John Miller, Deputy Commissioner of Intelligence and Counter-Terrorism for the NYPD spoke alongside Schumer.

He said the department’s new counter-terrorism squad is armed with assault rifles, and is a visible show of force in the city.

“Right now we are getting to a place where this city has never been before, where there will be over 1,500 officers on duty in the New York City Police Department who have special weapons and tactics training and that is a sign of the times,” he said.

The President also called on the American Muslim community to serve as a partner in the fight against radical Islam.

The spread of radical Islam, he said, is “a real problem that Muslims most confront without excuse.”

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Obama said Muslims can send credible, effective counter messages and undermine jihadist propaganda.

The president implored Americans to not turn against Muslims at home, saying the Islamic State was driven by a desire to spark a war between the West and Islam.

The president announced no significant shift in U.S. strategy and offered no new policy prescriptions for defeating the Islamic State, underscoring both his confidence in his current approach and the lack of easy options for countering the extremist group. He did call on Congress to tighten America’s visa waiver program and to pass a new authorization for military actions underway against IS in Iraq and Syria.

“I’ve ordered the departments of state and homeland security to review the visa waiver program under which the female terrorist in San Bernardino originally came to this country,” he said.

One of the shooters, Tashfeen Malik was born in Pakistan but was in the U.S. on a fiance visa for her marriage to Syed Farook.

“We’re going to have to look at all visas. Right now there is bipartisan legislation working in the Senate and House to make sure the visa waver program is tightened up, that’s the real danger here,” Schumer said.

Obama added that he wants stronger screening for those who come to the U.S. without a visa to see if they’ve traveled to war zones.

With the prime-time address, Obama turned to a tool of the presidency that he has used infrequently. He’s made televised statements from the Oval Office just twice, the last in 2010.

A woman held responsible for last week’s shooting in San Bernardino, California, had, under a Facebook alias, pledged allegiance to IS and its leader, according to U.S. official who was not authorized to discuss the case publicly and spoke on condition of anonymity. A Facebook official said the post came about the time the couple stormed the San Bernardino social service center.

Authorities said the woman – a 29-year-old originally from Pakistan – carried out the attack with her 28-year-old American-born husband, killing 14 people and wounding 21. The two were killed in a shootout with police hours after the attack.

Authorities say they believe the guns used by the attackers were legally obtained.

The FBI is investigating the massacre as a terrorist attack that, if proved, would be the deadliest by Islamic extremists on American soil since Sept. 11, 2001.

FBI Director James Comey has said there was no indication yet that the plot was directed by any other foreign terrorist group, though he would not rule out that future possibility.

Obama initially said the shootings could have been terrorist-related or an incident of workplace violence. Two days later, in his weekend radio and Internet address, the president said called the attacks an “act of terror” and said it was “entirely possible that these two attackers were radicalized to commit this act of terror. And if so, it would underscore a threat we’ve been focused on for years – the danger of people succumbing to violent extremist ideologies.”

Lynch said the kind of threats against the United States has evolved because the government has been able to foil plots. “We have come from a time of the large-scale planned al Qaeda-style attacks to the encouragement of lone wolves.’

Some of the Republican presidential candidates had quickly labeled the shootings an act of terrorism and faulted Obama for not saying so immediately. GOP candidates have sought to equate the president’s cautious language on terrorism with what they see as his tepid approach to national security.

“I don’t know why the president hesitates for so long to call it exactly what it is,” New Jersey Gov. Chris Christie said.

Florida Sen. Marco Rubio called on Obama to outline a more robust strategy for defeating IS, which has strongholds in Iraq and Syria. Rubio advocated a “ground force made up primarily of Sunni Arabs from the region, including Iraqis and Syrians, but also a contribution of troops from Jordan, Saudi Arabia, Egypt.”

Hillary Clinton, the front-runner for the Democratic presidential nomination, said the U.S. is “not winning” the fight against IS and it’s “too soon to say that we are doing everything we need to do.” While Clinton has been supportive of Obama’s foreign policy, given that she served as his secretary of state, she also has called for a more robust approach to defeating IS, including setting up a no-fly zone.

The president’s approach has relied largely on airstrikes by the U.S., as well as European and Arab partners. He has struggled to identify and train effective forces on the ground to supplement those efforts and has ruled out a large scale deployment of American troops.

Christie spoke on CBS’ “Face The Nation,” Rubio was on CNN’s “State of the Union” and Clinton appeared on ABC’s “This Week.”

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