WASHINGTON (Reuters) - U.S. strikes on Afghanistan (news - web sites) may prompt the al Qaeda network to activate some long-planned plot against American targets and U.S. intelligence agencies were on high alert, officials said on Sunday.
``There will be more strikes by terrorists against U.S. interests, whether it's here or abroad or both remains to be seen,'' one official told Reuters on condition of anonymity.
``There are lots of potential threats out there and there is little doubt that they are going to do something,'' the official added. ``They have been killing Americans for a number of years and were going to continue doing it whether we did this or not.''
U.S. and British forces launched air strikes on targets across Afghanistan that included military positions of the country's ruling Taliban and training camps of militant Osama bin Laden (news - web sites)'s al Qaeda network.
The United States has said bin Laden and his group backed the Sept. 11 attacks on New York and Washington that left nearly 5,600 people dead or missing.
Al Qaeda's method has been to have a plot planned long in advance with the network more likely to activate such a plan rather than formulate a new one to respond to Sunday's strikes on Afghanistan, U.S. officials said.
``Most of the kinds of attacks that we've seen tend to have been planned months and months and months, in some cases years in advance,'' Defense Secretary Donald Rumsfeld said.
Other U.S. officials said Al Qaeda was likely to decide to go to such a plan.
``Their MO (modus operandi) is to have plans in place long in advance, so they're not going to come up with a new plan as a result of this,'' the U.S. official who spoke on condition of anonymity said.
``They might time their next response in light of this, it's hard to say. Now that this has happened they can say 'OK, the next thing in our playbook let's go to it now,' but they were going to go to it anyway,'' the official said.
U.S. WARNS CITIZENS
The U.S. government warned its citizens overseas to be on heightened alert because the strikes may lead to strong anti-American sentiment, and the Federal Aviation Administration (news - web sites) said it was working closely with air carriers to ensure maximum safety at the nation's airports.
President Bush (news - web sites) said, ``Our government is taking strong precautions. All law enforcement and intelligence agencies are working aggressively around America, around the world and around the clock.''
He said at his request many governors had activated the National Guard to strengthen airport security.
``We have called up reserves to reinforce our military capability and strengthen the protection of our homeland,'' the president said.
The State Department advised Americans to leave Afghanistan and Americans elsewhere to maintain contact with the embassy.
``This action may result in strong anti-American sentiment and retaliatory actions against U.S. citizens and interests throughout the world by terrorists and those who are sympathetic to or otherwise support terrorism,'' a State Department announcement said.
Rumsfeld said the strikes on Afghanistan had not targeted bin Laden, but were aimed at terrorist networks.
``This is not about a single individual, it's about an entire terrorist network and multiple terrorist networks across the globe,'' he said.
``The only way to deal with these terrorist threats is to go at them where they exist. You cannot defend at every place, at every time, against every conceivable, imaginable, even unimaginable terrorist attack,'' Rumsfeld said.
The U.S. official said the ``entire national security establishment from intelligence to law enforcement to the Pentagon (news - web sites) is all engaged in a way that I've never seen before.''
There were ``lots of threats, rumors, reports, we take them all seriously,'' the official said, adding that the intelligence cooperation from different countries has been ``unprecedented in its nature.''
``We have received more assistance than we've ever received before, but we need much more,'' the official said.