Washington (CNN) The waiver program that allows citizens from some countries to enter the United States for up to 90 days without a visa is "the Achilles heel of America," Sen. Dianne Feinstein said on Sunday.

The California Democrat and former Senate Intelligence Committee chairwoman's comments, on CNN's "State of the Union," come on the heels of the Paris attack on the satirical newspaper Charlie Hebdo.

Feinstein noted that the suspects in the attack were French citizens -- and people from France can enter the United States without visas. The suspects were on a no-fly list, but she said they could obtain a false passport or find some other way to go unnoticed.

She said other terrorists will likely do just that, if they haven't already.

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