The White House's Delicate Veto Dance on Landrieu's Keystone Bill

President Obama's administration has repeatedly reminded the public that he does not support legislation to approve the Keystone XL pipeline, but officials continue to keep coy about whether he would veto it.

"It certainly is a piece of legislation that the president doesn't support," White House spokesman Josh Earnest said during a briefing on Tuesday when asked whether Obama plans to veto the bill.

The White House has hinted that it will veto the legislation backed by Democratic Sen. Mary Landrieu throughout the week. But Earnest's statement indicating that the president does not support the bill represents the White House's strongest stance yet.

Yet while the White House played coy on Tuesday when reporters asked Earnest whether the president would veto pro-Keystone legislation if it passes, the administration did not hesitate to speak its mind on a slate of Republican-backed House bills this week.

The White House issued a formal veto threat on Monday directed at a trio of House bills that would tamp down on the Environmental Protection Agency's ability to roll out new regulations.

Obama did not issue a veto threat when the House passed its own pro-Keystone legislation on Friday, however. And Earnest said Tuesday that the White House currently has no plans to roll out a veto threat for the Senate's pro-pipeline legislation, though he noted that could change.

Despite the lack of a formal threat, Earnest strongly indicated the president would block the legislation if it crosses his desk.

"The president has been very clear about what our views are as it relates to Keystone," Earnest said, adding: "There is a process that's underway that is currently going through its regular course."

But if the White House wanted to be more clear, it could do what it did with a trio of energy and environment bills moving through the House this month. For all three measures, the White House's Office of Management and Budget on Monday issued an official statement of administration policy in opposition. All three ended with the same line: "If the President were presented with [the legislation], his senior advisors would recommend that he veto the bill."

Thus far, OMB has issued no such pronouncement on Landrieu's pro-Keystone measure, and the lack of a formal veto threat highlights the pipeline's tricky politics for Democrats.

Environmentalists have long called on the administration to reject the pipeline, which would ship heavy crude from Canada to Gulf Coast refineries. But the project is popular with blue-dog Democrats and labor unions, another key constituency in the Democratic base.

The decision is all the more complex because of the current Louisiana Senate runoff race between Landrieu and Rep. Bill Cassidy. Landrieu has pushed hard for a vote on the pipeline bill, and insists she has assembled 60 votes necessary to move it forward. She is betting that securing passage of the Keystone bill would boost her chances in the fossil-fuel-rich state.

The State Department is currently reviewing the pipeline, and Secretary of State John Kerry has yet to make a final recommendation as to whether it should be approved.