CHICAGO -(Dow Jones)- Navistar International Corp. (NAV) said it's opposed to delaying its court challenge of federal guidelines for complying with new, tougher standards for diesel-engine exhaust.

The U.S. Environmental Protection Agency late last month asked a federal appeals court to postpone proceedings on Navistar's case for 60 days while the agency reconsiders its compliance guidelines. The court hasn't yet ruled on the EPA's request. Navistar is scheduled to file initial briefs in the case Nov. 20.

In a court filing late Monday, Navistar said the EPA's request for a stay is " a pointless strategic maneuver" because the agency has given no indication that it's willing to withdraw its approval of selective catalytic reduction, or SCR, as a strategy for reducing nitrogen-oxide levels in diesel-engine emissions.

Navistar's case being closely watched by U.S. truck and engine makers because SCR is the preferred approach in the industry for meeting the EPA's 2010 emissions standards for diesel engines.

"If the EPA genuinely wants to change the result ... Navistar would support the motion [for a delay] rather than oppose it," the Illinois company said in a filing with U.S. Court of Appeals in Washington D.C. "EPA has known that tinkering with the guidances will not address the issues Navistar has raised in this litigation."

Navistar has accused the EPA of disregarding its own procedures and analysis in certifying SCR, which subjects diesel exhaust to a urea solution to reduce nitrogen-oxide pollution. Navistar is only truck maker in the U.S. not planning to use SCR on its engines next year. The company also alleges the EPA allowed truck and engine makers using SCR to exert unprecedented influence over the EPA's guidelines for SCR.

Navistar particularly objects to an EPA provision allowing commercial trucks with SCR to operate for up to 1,000 miles once the urea solution has been used up. After that, the truck's engine would become inoperable. Navistar contends truckers could undermine the effectiveness of the new emissions regulations by repeatedly invoking the 1,000-mile exemption on SCR-equipped engines.

Navistar's battle against selective catalytic reduction has attracted scorn from rival truck and engine manufacturers. Cummins Inc. (CMI) Chairman and Chief Executive Tim Solso last week described Navistar as "grasping at straws" in challenging the guidelines for using SCR.

"It's our view that the case has no merits and will not succeed in any way," said Solso during a conference call with analysts. "The EPA is holding all the cards here."

Navistar was last trading up 2.52% at $35.80 a share.

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