(AP) -- Sen. Charles Schumer proposed a federal law Monday that carries up to five years in prison for scaling prominent national structures such as the World Trade Center, Statue of Liberty and Golden Gate Bridge.

Schumer says his state is the nation's top terror target. His proposed maximum sentence of five years is a considerable jump from the one year in New York City's trespassing law.

Recent incidents include a Russian tourist who climbed the Brooklyn Bridge, two German artists who claimed responsibility for replacing American flags with mysterious white ones atop the famed span that links Manhattan and Brooklyn, and three extreme-skydiving daredevils who leaped off 1 World Trade Center.

"With terror threats at a high, it must be made loud and clear to any would-be trespassers, adrenaline junkies or potential criminals that the federal government and the New York Police Department take trespassing on critical infrastructure and national monuments very seriously," the Democratic senator said, standing near the Manhattan side of the Brooklyn Bridge with the city's deputy police commissioner for intelligence and counterterrorism, John Miller.

In New York, the maximum federal sentence of five years also would apply to the Statue of Liberty, various tunnels and the suburban Indian Point nuclear power plant north of the city -- all considered critical infrastructures.

They're defined as physical systems and assets so vital to the United States that their incapacity or destruction would have a debilitating impact on physical and economic security, or on public health.

The Russian climber was arrested in August after walking on a bridge landing while taking photos with his cellphone. A prosecutor initially offered him a deal of 90 days in jail, but a judge ordered a community service penalty.

Earlier in the summer, the two Berlin-based men said they replaced the bridge flags with bleached-out versions as a tribute to public art.

The city's Department of Transportation has installed new barriers on the bridge to prevent anyone from climbing up.

The teen who climbed 1 World Trade Center last spring was sentenced to 23 days of service plus youth counseling after admitting he broke a city misdemeanor law against scaling tall buildings without permission. He later climbed a New Jersey water tower -- also considered critical infrastructure.

Just days before the 9/11 attacks, a daredevil Frenchman trying to use a motorized parachute to land on the Statue of Liberty's torch got snagged on the gilded flame, clinging to Lady Liberty's arm until police rescued him and slapped the handcuffs on.