The first bill of the Republican-controlled Senate seeks to approve construction of the long-delayed pipeline. Democrats and Republicans plan to use the debate, which is expected to drag into next week, to score political points.
Sen. Bernie Sanders, a Vermont independent, said Tuesday he'd offer an amendment that would have Congress acknowledge global warming is real and is caused by human activities. It also says the U.S. must move away from fossil fuels as rapidly as possible.
Sen. Edward Markey, D-Mass, said he'd push for an addition to the bill that would bar oil from the pipeline, and block the gasoline and other products refined from it, from being exported.
Both are expected to be longshots in a Senate controlled by Republicans, many of whom question the scientific consensus on global warming, and who said they were readying another measure to lift a ban on crude oil exports.
"That oil should not come to our country, go right through it, and out," Markey said. He and other Democrats also hinted that they'd seek to close a loophole that exempts tar sands oil imported into the U.S. from being taxed for an oil spill cleanup fund.
Full-blown debate on the bill continued Tuesday after the Senate agreed 63-32 Monday to begin deliberating the measure.
Sen. John Hoeven of North Dakota, the lead Republican sponsor of the measure, said that the additions will "help us build the right kind of energy plan for our country."
But Sen. Maria Cantwell of Washington, the top Democrat on the Senate energy committee, said the bill represents 19th century energy policy, not the clean energy that should be embraced in the 21st century.
The 1,179-mile pipeline would carry an estimated 800,000 barrels of crude oil a day from Canada to Nebraska, where it would connect with existing pipelines on its way to Gulf Coast refineries.
The bipartisan 63-32 vote was 3 more than the 60 required, and well above the level the measure ever gained in recent years when Democrats controlled the Senate. But Republicans will need to secure more Democratic support to override a veto, as has been repeatedly threatened by the White House.
The measure has sparked intense debate over the Canada-to-Texas pipeline's potential impact on employment and the environment. While the project was proposed six years ago, the White House opposes the legislation as long as the administration is still conducting its formal review.
But with more than enough votes at their command, Republican and Democratic supporters said they hoped the legislation could win final approval and be sent to the White House by the end of next week.
Republican leaders were anxious to get started Tuesday.
"We support an open process but not an open-ended one," said Senate Majority Leader Mitch McConnell of Kentucky, who urged Democrats to file their amendments and said "we won't be dissuaded from our path."