CHICAGO -- Navistar International is opposing the U.S. Environmental Protection Agency's request to postpone court proceedings on Navistar's lawsuit against the agency.

Navistar -- which, as it's well known by now -- is the only major truck OEM not using selective catalytic reduction (SCR) technology in upcoming 2010 engines. It is suing the EPA for what it claims is the agency's betrayal of the agency's own stance in a official guidance issued 2001 that SCR would not be a feasible technology.

In particular, Navistar contends EPA is improperly allowing SCR systems to incorporate a 'ramped shutdown' feature in case the diesel exhaust fluid (DEF) required for SCR engines runs dry. Navistar likens this allowance to a "licence to pollute" and "pollution for convenience."

In late October, the EPA asked a federal appeals court to grant a 60-day stay (which, incidentally, would expire just as the Jan. 1, 2010 emissions regulations take effect). The delay would give the agency time to revise the original guidance in order to address Navistar's concerns, EPA says.

In court filings, EPA also mentioned that the 2001 guidance is not binding and was only meant to advise truck OEMs of potentially acceptable solutions that could meet the agency's 2010 emissions regulations.

According to the Wall Street Journal, Navistar responded to the EPA's request by calling it "a pointless strategic maneuver."

"EPA has known that tinkering with the guidances will not address the issues Navistar has raised in this litigation."

Navistar's opposition to SCR as an approved 2010 engine solution has led to some heated exchanges between the Chicago-based company and its competitors in the heavy-duty truck market.

This past summer, Navistar attempted to block rival truckmakers from intervening in the suit against EPA. 

In response, officials from pro-SCR manufacturers privately questioned Navistar's staunch opposition to SCR when the company is using that technology in international markets.

The appeals court has yet to rule on the EPA's request for a stay.