OKLAHOMA CITY — While the debate continues over whether the United States will approve a proposed oil conduit from Canada to the Gulf Coast, the segment from Cushing, Okla., to the Texas Gulf Coast is halfway toward completion and could be transporting oil by the end of the year.

President Barack Obama traveled to Oklahoma nearly a year ago to tout construction of TransCanada’s Keystone XL pipeline from the Cushing oil hub to Houston-area refineries. A decision on whether to allow the longer pipeline awaits the results of a U.S. State Department review that is necessary because the oil would be carried across an international border.

Nearly 4,000 workers in Oklahoma and Texas are aligning and welding a 485-mile section, TransCanada spokesman David Dodson told The Associated Press.

“We’re right at peak right now,” he said. “We hope to have it in operation by the end of this year.”

TransCanada applied for a federal permit almost five years ago but its construction has become controversial. Environmentalists warn of potential spills and say extracting and using tar sands oil, which the pipeline would carry from Alberta, would worsen climate change. Unions and TransCanada counter the project will bring thousands of jobs and bolster the United States’ oil supply from its friends and neighbors.

Obama rejected the permit early last year but left the door open for a retry that the State Department is currently considering. A decision could come by summer.

Because the Gulf Coast segment doesn’t cross an international border, its approval process was much simpler and work began last August, Dodson said. When completed, the segment will carry 700,000 gallons of oil each day from the existing pipeline network centered around Cushing to the southern refineries.

Now about 850 laborers are at work in Oklahoma, with roughly 3,000 more in Texas. Most are temporary contracts. Dodson said he didn’t know when those numbers would start winding down.

Pipeliners Local 798, a national union based in Tulsa, Okla., has about 250 of its members working on the pipeline’s northern two-thirds, union business manager Danny Hendrix said. He estimated about half of those welders are from Oklahoma.   

“These jobs are really good-paying jobs,” Hendrix said. “They provide not only a good living wage, they provide health care and they also provide pension.”

Throughout the approval process, TransCanada has stressed those benefits, saying the pipeline could support thousands of people in economically rough times. Hendrix said the jobs were appreciated but not as urgent as they’ve been portrayed.

“All that being said, here’s the deal: We’ve been very fortunate in the pipeline business,” he said. “When the rest of the economy was in terrible shape, we’ve been doing very well. It’s not a deal breaker or a killer for us if we don’t get it.”

Work started in Oklahoma about two months ago. Dodson, from TransCanada, said protests against it — formerly limited to Texas — have come with it. At least two so-called “direct actions” involved people locking themselves to construction equipment to prevent its use, leading to 10 arrests in central Oklahoma.

Such civil disobedience tactics have become a mainstay of the pipeline’s opposition. A rally near the White House on Feb. 17 drew 35,000 protesters, according to organizers, a few days after celebrities and prominent environmental activists tied themselves to the White House fence.

“What we’re working on — and experiencing some success with — is trying to amplify the voices of people who aren’t represented by the national discourse,” said Jay Morris, a spokesman for the Great Plains Tar Sands Resistance in Oklahoma. Those people include those living at both ends of the Keystone XL proposal, he said: where the oil is extracted and where it’s processed and refined.

Protests will continue, Morris said, and his group will keep trying to unify opposition even if the Keystone XL pipeline is finished from Canada to Texas.

In the meantime, Hendrix said, pipeline workers with his union will keep an eye on Washington.   

“If the permit gets approved, we’ll start construction on the northern end of it immediately,” he said.