The White House has agreed to streamline the sharing of intelligence and operational military information with French authorities, one of several efforts aimed at countering Islamic State extremists since last week's deadly Paris attacks.
President Obama announced the agreement Monday at the Group of 20 summit in Antalya, Turkey, telling reporters that the new arrangement "will allow our personnel to pass threat information, including on [Islamic State], to our French partners even more quickly and more often."
He did not provide details, but officials said France will gain access to communications intercepts and other raw intelligence at a level close to that provided to America's English-speaking allies: Britain, Canada, Australia and New Zealand.
British Prime Minister David Cameron announced separately that his government plans to boost its spying capability significantly by recruiting a total of 1,900 more intelligence officers for MI5, Britain's domestic security outfit; MI6, its foreign spy agency; and Government Communications Headquarters, or GCHQ, which conducts electronic surveillance.
In Washington, CIA Director John O. Brennan said he is seeking to strengthen counter-terrorism intelligence sharing with Russia, especially on Islamic State. He told a Washington think tank that he had spoken several times to his Russian counterpart in recent weeks in a new push to stop militants from the Caucasus from heading to Syria and Iraq.
Atty. Gen. Loretta Lynch separately said at a news conference that the Justice Department will "ramp up our defenses" in the United States, although she provided no new details.
The FBI previously said it has open investigations in every state on U.S. citizens who are believed to be communicating with militants overseas, who are considering trips to Syria, or who may be planning violence on U.S. soil. Several dozen Americans have been arrested on charges of providing material support to Islamic State in the last year.
"We have far fewer people who make that effort than in Europe," Lynch said. "But it is still something we take extremely seriously, and there are a number of cases against individuals who have attempted to leave and provide material support in Syria."
The moves come as U.S. and allied intelligence and law enforcement services scramble to piece together the Paris plot, which left at least 129 dead and hundreds injured, and to determine whether Islamic State has other violent plots "in the pipeline," as the CIA chief put it.
Speaking at the nonpartisan Center for Strategic and International Studies, Brennan warned that European intelligence agencies are overwhelmed by the need to identify and monitor potential terrorism suspects.
European authorities face "an overwhelming number of cases they need to pursue," Brennan said.
He also warned of a black market in military assault rifles like those used in Friday's massacre in Paris. Criminal networks in Europe have obtained AK-47s and other weapons looted from armories "that were overrun in the 1990s in Eastern Europe" after the fall of the Iron Curtain, Brennan said.
By far, the biggest threat appears to be from the thousands of Europeans who have joined militant groups in Iraq and Syria in the last few years. Officials fear they could return to their home countries to launch attacks, just as several of the assailants in Paris reportedly did.
British officials say they have disrupted seven terrorist plots in the last year, and an estimated 700 British nationals have gone to fight in Syria and Iraq. French intelligence services say about 1,800 French citizens have gone since 2011. More than 2,000 Russians are believed to have joined the conflict as well.
"The sheer number of fighters that have gone over and traveled to Syria and Iraq is unprecedented in jihadist battlefields in the modern era," Seth Jones, a former U.S. counter-terrorism official now with Rand Corp., said in an interview.
Adding to the challenge, militants have increased their use of encrypted text messaging apps on cellphones in recent months, creating new blind spots for U.S. and European security services trying to disrupt potential plots.
French and British intelligence agencies have "pretty intrusive" domestic surveillance, Jones said, tapping phones and monitoring neighborhoods. But security services in Belgium are less aggressive, which may explain why plans for the Paris attacks appear to have been hatched there.
"If you want to stage an attack in Paris, but you think French security services are just too good in France, you do your initial plotting in Belgium," Jones said.
A purported Islamic State video posted online Monday warned of more violence in Europe, and specifically threatened Washington.
"I say to the European countries that we are coming, coming with booby traps and explosives, coming with explosives belts and [gun] silencers and you will be unable to stop us because today we are much stronger than before," a militant says in the video, which appears on a site used by Islamic State to post its messages.
Another militant in the video says that "as we struck France in the center of its abode in Paris, then we swear that we will strike America at its center in Washington."
It was not immediately possible to verify the authenticity of the video, which purports to be the work of Islamic State fighters in the Iraqi province of Salahuddin, north of Baghdad.
Times staff writers W.J. Hennigan and Timothy M. Phelps in Washington contributed to this report.
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