PITTSBURGH (AP) -- United States Steel Corp. said Thursday it is delaying indefinitely a $1 billion upgrade of a coke plant near Pittsburgh to cut costs as the global economic downturn saps demand for steel.

The Pittsburgh-based company has said the project at the Clairton plant was expected to create more than 600 construction jobs and ensure thousands of existing jobs. The improvements were meant to reduce environmental emissions at the plant, the country’s largest production facility for coke -- coal that’s baked and used as a fuel in steel making.

The move was another indication of the toll taken on steel companies by the global economic crisis. U.S. Steel has laid off thousands of workers since late last year, when demand and prices plummeted for the metal used in everything from autos to appliances. Last year’s sudden slump came just weeks after some steel makers posted record profits.

“The ongoing global economic crisis has forced the company to make difficult but necessary decisions in all areas of our operations,” the company said in a statement. “These conditions have forced us to delay the Clairton Investment Program and we cannot speculate as to when conditions will improve enough to allow work to resume.”

The company broke ground on the project in October. It was expected to include the construction of two new coke batteries, or sets of ovens, that would replace groups of aging batteries and the rehabilitation of other batteries.

The plan also included lowering the number of coke ovens by 235 and reduce by 30 percent the number of openings through which emissions might pass.

Shares of U.S. Steel rose $1.97, or 8.7 percent, to $24.59 in morning trading Thursday.