President Barack Obama made it clear on Tuesday that he would veto a bill to approve the controversial Keystone XL pipeline after Republicans introduced legislations to approve it as their first order of business for the new Congress.

The White House threatened to veto legislation approving the pipeline, which is one of the top items on the Republican agenda now that they control both branches of Congress.

"If this bill passes this Congress, the president wouldn't sign it," White House Press Secretary Josh Earnest said Tuesday, according to Fox News.

Instead, Earnest said that the president wants to wait for a State Department review process to finish. The Obama administration is also waiting for a court in Nebraska to issue a ruling on the pipeline's route.

"There's an important principle at stake here. There's a well-established process that should not be undermined," added the press secretary.

In response, House Speaker John Boehner slammed Obama for not supporting the bill.

"On a bipartisan basis, the American people overwhelmingly support building the Keystone XL pipeline. After years of manufacturing every possible excuse, today President Obama was finally straight with them about where he truly stands. His answer is no to more American infrastructure, no to more American energy, and no to more American jobs," he said, reports MSNBC. "Fringe extremists in the president's party are the only ones who oppose Keystone, but the president has chosen to side with them instead of the American people and the government's own scientific evidence that this project is safe for the environment. ... Obama is hopelessly out of touch and has no plans to listen to the American people or champion their priorities."

Environmentalists say that the pipeline would bring heavy tar sands oil from Canada across the middle of the United Sates to a port on the Gulf of Mexico. In turn, this will contribute to climate change and pollute the environment.

Republicans, however, argue that the pipeline will create jobs and reduce gas prices.

Still, Obama said at his year-end news conference that the benefits Republicans claim the pipeline will bring are inflated, and it would only increase temporary jobs for American workers.