The us is not raising its terror alert status.

美国目前没有提高反恐警戒线。

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The terror alert system, however, was not in effect at the time, but rather, implemented in 2002.

CNN: Experts question U.S. terror alert system

With Europe under an unprecedented terror alert, the U.S. State Department has issued a travel alert, warning of potential terrorist attacks.

FORBES: 10 Secret Service Survival Tips for Travelers

As we've been reporting, in the wake of today's bombings in London, US officials have raised the terror alert level for mass transit systems.

NPR: New York, Los Angeles Step Up Security