President Barack Obama on Sunday pledged to hunt down terrorists planning attacks on the United States as he sought to reassure Americans in the wake of last week's mass shooting in California.

"The threat from terrorism is real but we will overcome it," Obama said in a rare televised address from the Oval Office.

The president offered no policy changes, but instead expressed confidence in his administration's ongoing anti-terrorism strategy, and warned Americans against giving in to fear.

"We will destroy ISIL and any other organizations that try to harm us," he said, using an acronym for the "Islamic State" (IS) group.

"We will prevail by being strong and smart, resilient and relentless. And by drawing upon every aspect of American power."

Obama said the US military would continue to track terrorists overseas while working with a coalition of its partners in Iraq and Syria to fight IS militants, whom he described as "thugs and killers."

The president also said America should not be dragged into a costly and drawn-out ground war in the Middle East, saying that was what "groups like ISIL want."

'Brutal path of radicalization'

Obama's 13-minute speech comes after a couple opened fire at an office party in San Bernardino, California, on Wednesday, killing 14 people and wounding 21. The alleged killers, Syed Rizwan Farook, 28, and his Pakistani wife, Tashfeen Malik, 29, died in a shootout with police a few hours after the attack.

Obama said while there was no evidence to suggest the pair belonged to an organized terrorist group, they appeared to have "gone down the brutal path of radicalization."

He described the attack as a clear act of terrorism "designed to kill innocent people," and said it was a sign the war on terror had entered a "new phase."

On Saturday, IS - which claimed responsibility for killing 130 people in the Paris attacks last month - said the California shooting had been carried out by its "supporters." Authorities allege Malik pledged allegiance to the group in a Facebook post.

In his speech, Obama implored Americans not to alienate Muslims at home. He also said Muslims had a responsibility to confront "extremist ideology" that has "spread within some Muslim communities."

"We cannot turn against one another by letting this fight be defined as a war between America and Islam," the president said.

Renewed call for tighter gun control

The San Bernardino couple had allegedly stockpiled four guns, some 6,000 rounds of ammunition and a dozen pipe bombs before carrying out their attack. Authorities say they believe the guns were all legally obtained.

Obama renewed his plea for Congress to pass tougher gun control measures, including one that would bar people on the so-called no-fly list buying guns and making it harder for people to buy assault weapons.

"What we can do, and must do, is make it harder for them to kill," he said.

The president also called for stricter visa rules and a new authorization for military operations in Iraq and Syria. He added that he would request cooperation from tech firms to prevent potential attackers using technology to promote terrorism and escape detection.

Sunday's televised speech was only the third such address Obama has made from the Oval Office during his time as president. The last, in 2010, was to announce the end of combat missions in Iraq.

nm/jm (Reuters, AP, dpa, AFP)