Chanting ironically, "Yes we can" -- Barack Obama's 2008 campaign refrain -- the demonstrators want the administration and the U.S. State Department to block approval of the Keystone XL oil pipeline from Canada, saying it might prove a pollution disaster, Politico reported.
U.S. Park Police began making arrests Monday when protesters failed to disperse; only seven protesters left before being arrested.
As their fellows were being arrested, 65 demonstrators arrested Saturday were preparing to be released from jail, the newspaper said.
"We see this pipeline as the biggest environmental test President Obama will have before the 2012 election," Jamie Henn, a spokesman for jailed protest organizer Bill McKibbens' group Tar Sands Action, told Politico. "With the stroke of a pen, he'll be able to end a potential environmental disaster, stop the pipeline and electrify a base of support that hasn't been enthusiastic about his re-election."
Obama was on vacation with his family at Martha's Vineyard, an island off Massachusetts.
The protests began Saturday and are scheduled to continue for two weeks, Politico said.
The proposed pipeline would carry oil-sands-based crude 1,700 miles from Alberta, Canada, to refineries in Texas, the newspaper said.