WASHINGTON — U.S. Park Police on Sunday arrested hundreds of demonstrators participating in an act of civil disobedience to protest the proposed Keystone XL pipeline at the White House.

Organizers estimated that about 450 people — mostly college students — would ultimately be arrested as they tried to dissuade the Obama administration from approving the 1,700-mile crude-oil pipeline from Canadian oil sands to the Gulf Coast.

“Hey, Obama, we don’t want no climate drama,” the protesters chanted, as they attached their hands to the fence in front of the White House with plastic zip ties. Others lay down on a plastic tarp representing a “human oil spill,” some wearing plastic suits with a skeleton and a woman in a Captain Planet costume.

The protesters were mostly students who participated in a peaceful march that began at Georgetown University.

The Keystone XL pipeline has become a touchstone for the environmental movement, and civil disobedience has been a key tactic: 1,200 were arrested at the White House over two weeks in fall 2011, and smaller-scale actions have taken place around the country.

More than 86,000 people signed a “Pledge of Resistance” promising civil disobedience if a State Department report expected in the coming months points toward approval.