Prime Minister Stephen Harper's pledge to ship oil sands crude to China, should Keystone XL get kiboshed, is pure political grandstanding, a lead U.S. environmental organizer argues.

"I think he is kind of trying to bluff," Bill McKibben told a crowd of dozens Monday night at the Occupy Vancouver encampment.

McKibben is a long-time environmental writer who founded 350.org, a global campaign to fight climate change.

He's recently become somewhat of a hero in green circles for leading massive protests against TransCanada's Keystone XL.

Those protests likely played a role in the Barack Obama administration's recent decision to delay the pipeline by up to 13 months.

Wearing a blank baseball cap and yellow scarf, the 50-year-old McKibben told Vancouver occupiers there's now more pressure than ever for them to oppose both Enbridge's Northern Gateway pipeline and Kinder Morgan's competing pipeline expansion.

"It's incredibly important for you guys to figure out all the ways you can to stop them," he said to scattered cheers and twinkling fingers.

Canada's federal government has effectively shrugged off recent Keystone XL delays, saying it will merely focus on shipping Alberta's oil sands crude to China and beyond.

"Canada must increase its efforts to ensure it can supply its energy outside the United States and into Asia in particular," Prime Minister Harper told reporters this week in Honolulu.

Already, at least one major U.S. environmental group says it will fight Enbridge's plans to build a pipeline across B.C.

The Natural Resources Defense Council claims that more than 60,000 of its members and supporters have sent emails opposing the project to Premier Christy Clark.

McKibben told The Tyee in an interview he'll provide any support necessary to Canadian activists, but won't take a lead role in the fight.

"I'm an American," he said. "Canadians don't want me coming up here and telling them what to do."

Geoff Dembicki reports on energy and climate issues for The Tyee.