By Steve Holland and Erin McPike
WASHINGTON (Reuters) - U.S. Republican presidential candidates on Thursday rushed to describe a mass shooting in California as a sign that Americans are at risk from homegrown Islamic militants, seizing on the country's deadliest massacre in three years before a motive had been firmly established.
Candidates spoke to the Republican Jewish Coalition's annual conference to warn of the threat from Islamic State militants and pledge to take steps against the group, a sign of how the deadly Paris attacks last month have transformed the campaign running up to the November 2016 election.
"There can be no doubt that this is an effort to destroy our very way of life," said Republican John Kasich, the governor of Ohio.
Many candidates were quick to link the killing of 14 people in San Bernardino, California on Wednesday to the possibility of homegrown radicals. It was the deadliest shooting in the United States since 20 children and six adults were killed by a gunman at the Sandy Hook Elementary School in Newtown, Connecticut in December 2012.
"If a center for the mentally disabled in San Bernardino, California, can be a target for a terrorist attack, then every place in America is a target for a terrorist attack," said New Jersey Governor Chris Christie. "We need to come to grips with the idea that we are in the midst of the next world war."
A motive for Wednesday's attack is far from clear. The head of the Federal Bureau of Investigation's Los Angeles Field Office probing the shooting said on Thursday it would be "irresponsible and premature" to say that terrorism was the motive.
Authorities are trying to determine whether the couple accused of the killing, Syed Rizwan Farook and Tashfeen Malik, had links to Islamic militant groups abroad. The two were killed in a shootout with police after Wednesday's massacre.
President Barack Obama said the gunfire that erupted at a holiday party was possibly "terrorist-related" but could have been the result of a workplace dispute.
Texas Senator Ted Cruz joined the criticism, saying Obama had failed to take steps to protect the United States and declared it is time for a "war-time" president.
Real estate mogul and reality TV personality Donald Trump, who leads polls of Republican voters, said the California attack was likely related to what he called "radical Islamic terrorism." He faulted Obama for refusing to use that term.
"There's something going on with him that we don't know about," said Trump, who has repeatedly sought to raise doubts about whether Obama was born in the United States. Obama in 2011 produced his birth certificate to prove he was born in Hawaii.
Contrary to Democrats, who have called for tougher gun laws to prevent violent attacks, Cruz announced plans to hold a "Second Amendment" event in Iowa on Friday, in reference to the U.S. constitutional right to bear arms.
Candidate Carly Fiorina, a former Hewlett-Packard CEO, said in an interview on Fox News ahead of her speech Thursday that "everything points to a terrorist attack, a homegrown terrorist attack" in San Bernardino.
Both former Florida Governor Jeb Bush and Florida Senator Marco Rubio were careful not to declare the California attacks the result of homegrown jihadists while it was still being investigated. Bush led the crowd in a moment of silence for the victims.
Rubio said the West is waging war against radical "apocalyptic Islam."
"We must not separate the threat to Jerusalem and Tel Aviv from the threat to Paris or London or New York or Miami," Rubio said.
South Carolina Senator Lindsey Graham, a foreign policy hawk who wants to send more American troops to Iraq, said he would pursue an aggressive policy against Islamic State and "kill every one of these bastards that we can find."
(Additional reporting by Emily Stephenson and Ginger Gibson; Editing by Bill Trott and Bill Rigby)