Critics of the proposed Keystone XL pipeline interrupted President Obama's speech on health care in Boston Wednesday, demanding that he reject the controversial pipeline.

Keystone XL has emerged as a touchstone in the climate change debate since the pipeline was first proposed more than five years ago. But the topic is regularly sidelined by the news of the day – particularly in recent months as government shutdowns and debates over health care have dominated headlines.

Activists used Wednesday's forum as an opportunity to put the Canada-Texas pipeline back in the spotlight, interrupting his speech twice, but it's unclear what kind of lingering effect such a stunt might have on either the president's or the public's view on the proposed pipeline.

"Stop the Keystone pipeline," the protesters chanted from the aisles of Faneuil Hall, as the president defended the Patient Protection and Affordable Care Act. The health-care program has come under scrutiny for technical problems relating to its website, among other issues in its bumpy rollout.

Mr. Obama smiled and paused to allow the protesters to finish.

"That is the wrong rally. We had the climate change rally back in the summer," he quipped after the first interruption, perhaps referring to a large demonstration in Washington that drew tens of thousands to the National Mall in February. "This is the health-care rally." Once the protesting subsided, he resumed his speech.

It's perhaps a sign of frustration from environmentalists who have been petitioning Obama to reject the presidential permit required to build the transnational pipeline, which would transport heavy crude oil from Canadian tar sands to refineries in Texas. Opponents say the pipeline would increase US carbon emissions and poses the risk of oil spills.

Obama has been relatively mum on the subject, save during his June speech on climate change in which he said he'd only approve the pipeline if it did not significantly increase carbon emissions.

Backers of the pipeline have also expressed frustration with the permitting process, which has involved a handful of controversial government environmental reviews and is expected to continue at least into 2014. But TransCanada, the Canadian energy company behind the project, hasn't shown any signs of backing down from building the pipeline, or finding alternative ways to get the oil to market.

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“I think it’s clear that, [for] producers in both Canada and the United States, that the production decision is driven off ... global oil prices, not off pipeline infrastructure," TransCanada chief executive Russ Girling said Wednesday in an interview with The Hill. "As long as global prices support the development of the resource, it is going to get developed, and then it is going to get to market one way or another.”

Nearly two-thirds of Americans support the Keystone XL pipeline, according to a September poll by the Pew Research Center.