TXI, the largest cement maker in Midlothian, has withdrawn a request for state permission to burn about 145 million pounds of scrap tires a year as fuel for its cement plant in the Ellis County city south of Dallas.

The decision Tuesday by the Dallas-based company comes during a standoff between Texas officials and the Environmental Protection Agency. The EPA contends that parts of the state's air permitting system violate federal law.

Texas environmentalists have hailed the EPA pressure on the state as means of correcting what they call an industry-friendly permitting system. State environmental regulators say their system complies with federal law and protects the public from pollution.

TXI's tire-burning plan, which the company had already submitted and withdrawn once before during the summer, stirred objections from environmentalists and two Democratic legislators from Fort Worth, state Sen. Wendy Davis and state Rep. Lon Burnam. Scrap tires are an approved fuel for cement kilns, with the industry saying they emit less smog-causing nitrogen oxide than other fuels.

On Wednesday, the day after TXI dropped its permit application, Jeff Robinson of the EPA in Dallas wrote to the Texas Commission on Environmental Quality that the TXI tire-burning plan fell under a state program that the EPA says is inadequate.

The company was seeking authorization for the tire-burning plan under a standard permit for pollution control projects, a type of permit that allows for streamlined reviews and limited opportunity for public participation.

The EPA believes that letting major sources of pollution use the standard permit "does not fit within the scope or intent of our original approval" of the state permitting program, Robinson wrote.

To meet federal requirements, the EPA said, TXI would have to provide a detailed analysis of the tire proposal's effects on local emissions of nitrogen oxides, a contributor to ozone, or smog, and sulfur dioxide, responsible for acid rain.

"These increases were not adequately characterized ... in the withdrawn application" and appear to be big enough to trigger intense reviews under federal law, Robinson wrote.

Steve Hagle, director of the TCEQ's air permits division, said Friday that the state agency had already decided the application could not be approved as originally submitted.

"It was more of a matter of discussions back and forth," Hagle said. "They agreed not to do anything until we came to some conclusion about the application."

TXI spokesman David Perkins did not return phone calls for comment.