NEW YORK (TheStreet) -- Supporters of the controversial Keystone XL pipeline said they have the votes to pass a bill calling for its approval when the measure comes before the U.S. Senate late Tuesday. 

"We believe there are enough votes to pass it," said Don Canton, spokesman for Republican Sen. John Hoeven of North Dakota, a longtime Keystone backer who has cosponsored the bill, along with Democrat Sen. Mary Landrieu of Lousiana.

Canton predicted 45 Republicans and 15 or "perhaps" 16 Democrats will vote for the bill, achieving the margin of 60 votes needed to avoid a filibuster, halting debate in the Senate, which is expected to vote on the bill at about 6:15 to 6:30 p.m. EDT, Canton said.

Following passage in the House of an identical bill last Friday, the legislation would then to go President Obama, who is expected to veto it.

"The President has signaled clearly that he plans to veto it if it passes," Canton wrote in an email.

In the event of a presidential veto, supporters will reintroduce the bill in the new Congress, and attach it to a broader energy bill or to other "must-pass" legislation that the president won't want to veto, Canton said.

Republicans who have long called for presidential approval of Keystone launched a fresh initiative in the wake of their victory in the mid-term elections, introducing bills in both houses of Congress that would give the go-ahead for construction of the pipeline.

The pipeline, which would carry heavy crude oil from the tar sands of Alberta, Canada to refineries on the U.S. Gulf Coast, has been the focus of fierce confrontation between business interests, who say the project would generate jobs and boost energy independence, and environmentalists, who argue it would sharply increase carbon emissions and set back global efforts to slow climate change.

Beneficiaries of a completed pipeline would include Gulf Coast refineries such as Valero (VLO - Get Report) , which would have to pay less for piped crude than they do currently to ship it by rail, while forcing freight railroads to seek new customers, energy analysts have said.

Democratic supporters include Sen. Tom Carper of Delaware, who said he had decided to vote for the bill in an effort to break a partisan deadlock.

"The Keystone pipeline approval process has been long and difficult, and caught up in partisan politics for far too long," a spokesman said. "Senator Carper believes it is time to set politics aside and move forward in a bipartisan manner to address this complicated question."

By finding a bipartisan solution to Keystone, lawmakers may also be able to agree on solutions to other environmental and public-health threats posed by greenhouse gases, Sen. Carper's statement said.

His decision to support Keystone angered environmentalists in Delaware, who said the decision would mean continued shipments of Canadian crude to a Delaware refinery, and would heighten the risks posed by rising seas in the low-lying state.

"Carper's support for the Keystone XL pipeline and the import of tar sands to Delaware City is offensive to the hundreds of Delawareans who marched for climate action in NYC this September, and insulting to his constituents who are already feeling the impacts of sea-level rise," the local Sierra Club said in a statement.

At the time of publication, the author held no positions in any of the stocks mentioned.