The Keystone project has emerged as a defining issue for Obama, cast as a choice between the environment and the economy

This article is more than 8 years old

This article is more than 8 years old

Several thousand protesters, some shouldering a long black inflatable replica of a pipeline, formed a human chain around the White House on Sunday to try to convince Barack Obama to block the controversial Keystone XL project.

The protest, which had been weeks in the making, had been intended to put pressure on Obama to stop the pipeline, which would transport crude from the Alberta tar sands across the American heartland.

Organiser Bill McKibben described it as subjecting Obama to symbolic house arrest.

"That is the second biggest pool of carbon on the planet. If the US government goes ahead and makes it easier to develop that oil-sands project, then there is no credible way to insist that they're working hard on climate change," McKibben told the crowd.

Not that Obama was there to notice. As protesters gathered opposite the White House he took advantage of a glorious autumn day to go golfing, returning just as the protest was winding down.

A number of protesters carried blue signs quoting Obama's 2008 campaign promises to act on climate change. Others borrowed his election slogan, chanting: "Yes we can, stop the pipeline."

Organisers initially claimed a turnout of 6,000, later doubling the number to 12,000. They included the actor Mark Ruffalo, the climate scientist James Hansen and the Nobel peace prize winner Jody Williams.

Police said about 5,000 had come to the gathering.

The Obama administration had been due to decide on the fate of the pipeline by the end of the year. Over the last year, however, the Keystone project has emerged as a defining issue for Obama – cast as a choice between the environment and the economy.

Officials suggested this month that the deadline could slip. There could also be delays from a series of legal challenges along the pipeline's route. Legislators in the state of Nebraska this week are considering five separate bills to re-route the pipeline away from an important aquifer or challenge the company's rights to build over private land.

Environmental groups have warned Obama he could risk losing their support in the 2012 elections if he lets the pipeline go ahead. But that strategy is also a gamble for environmental groups.

A failure to persuade Obama would expose their own weaknesses.

TransCanada, the company building the pipeline, claims the project would create thousands of temporary construction jobs. "What these millionaire actors and professional activists don't seem to understand is that saying no to Keystone means saying yes to more conflict oil from the Middle East and Venezuela filling American gas tanks," James Millar, a spokesman for TransCanada said in an email.

"After the Washington protesters fly back home they will forget about the millions of Americans who can't find work."