– President Obama is being pressed by opponents of the Keystone XL pipeline to tie any approval to measures that would curb climate change, reflecting mounting pressure on the administration to mitigate the project’s effect if it proceeds.

Sen. Sheldon Whitehouse, D-R.I., is among those who want to see new steps to limit greenhouse-gas emissions in the United States if TransCanada Corp.’s petition to build the $5.3 billion pipeline to carry tar-sands oil from Canada to U.S. refineries is approved. Other lawmakers and those advocating more stringent climate-change protections say the administration could extract concessions from Canada, such as a higher carbon tax in Alberta, where the pipeline originates.

“He touted himself as the environmental president, and he’s going to have to make sure that if he decides to go with it that there is some kind of balance,” said Rep. Elijah Cummings, D-Md.

Most congressional Democrats, including leaders in the House and Senate, have joined environmentalists in fighting the project backed by the oil industry, labor unions, the Chamber of Commerce and Canadians. Some lawmakers who oppose the pipeline say it appears likely Obama will sign off, triggering their calls to mitigate environmental and political fallout.

In a deliberation that has stretched over four years, Obama first rejected the pipeline because its original route took it through Nebraska’s Sand Hills region, a national natural landmark. Calgary-based TransCanada changed the route and filed a new application, now under review by the State Department, which must act on pipelines crossing an international border.

Environmental groups dismiss a March draft assessment by the State Department that said the pipeline will not raise the risk of global warming, because the oil from Alberta would find its way to market with or without the line.

Decision due by end of year

A decision is expected by year’s end. The administration hasn’t said whether it could try to offset any approval with other environmental policy changes.

Secretary of State John Kerry, who fought for climate change legislation during 28 years in the Senate, may seek green offsets as part of the decision, although such action may be modest and unlikely to spark resistance from pipeline advocates, said two officials with knowledge of his thinking.

In Canada, Natural Resources Minister Joe Oliver has said his government isn’t designing upcoming oil and gas emissions rules to appease the United States on Keystone, although Alberta provincial officials say they’re discussing the possibility of stricter emissions standards.

Obama may have some offset options, said Daniel Weiss, director of climate strategy at the Center for American Progress, a Washington policy institute with ties to the administration. That includes making a firm commitment to issue new U.S. rules on limiting carbon emissions from existing coal-fired power plants, said Weiss, who opposes the pipeline.