A new delay emerged yesterday in the world's march toward common rules for trade and the environment. This time the hitch in globalization involved airplane noise.

The United States said it will file a formal legal complaint against the European Union for its decision to limit use of older commercial jets that have "hush kit" mufflers on their engines. This violates world rules on noise, U.S. officials contend, adding that what Europe is really trying to do is keep out American goods--hush kits are U.S.-made.

Not so, countered the European Union, calling the U.S. decision to file papers in coming weeks at the International Civil Aviation Organization a "most unhelpful step" in an already long dispute over hush kits. Despite their names, hush-kit planes are noise polluters, the Europeans contend, and don't deserve to keep flying.

Commercial jets sparked complaints about noise almost as soon as they first entered service in the 1950s. Pressed by governments, the aircraft industry has steadily been designing quieter planes and is phasing them into use under a global noise-abatement plan overseen by the ICAO, which has 185 member countries.

At issue now is compliance with the "Chapter 3" rules, due for final adoption in 2002. Big carriers have generally bought new planes that meet the rules; others, many smaller ones in the United States and in developing countries, have opted to upgrade older planes' engines to try to bring them into compliance. Hence the emergence of a hush-kit market.

The ICAO rules do not specify what method must be used but provide that certain noise standards must be met. The United States contends that complex tests show that hush kits meet the Chapter 3 noise levels. Europe contends that the tests don't reflect real-world conditions and the kits flunk.

With dense population patterns and airports near cities, engine noise is a major public and political concern in Europe. Last year, with broad support among citizens there, the European Parliament passed a law that would grandfather in hush-kit planes already operating in Europe, but block the introduction of more.

U.S. officials contend that this constitutes Europe changing rules the world has already agreed on. "It's a global industry, it has to stay global," said David Aaron, undersecretary of commerce for international trade, who went to Montreal yesterday to lay out the U.S. case to ICAO officials. "This kind of unilateralism cannot be part of it."

The fine print of the rule was written with a secret trade agenda, U.S. officials contend. "They drew this line . . . specifically so that it would exclude all American airplanes" using hush kits, Aaron said. "It's a transparent effort to only affect American equipment." If carriers have to buy new planes, the U.S. contends, that could mean more business for Europe's Airbus Industrie consortium.

Last March, Congress moved to give some teeth to U.S. demands. The House passed a measure to ban Europe's famously noisy Concorde supersonic jetliner from flying to the United States if the hush-kit ban goes forward. The plane has been operating here under a special waiver of U.S. noise rules. The measure is pending before the Senate.

The Europeans dismiss talk of protectionism and say they are the ones in line with ICAO principles, which call for adoption of best-available technology. Hush kits are a less effective, stopgap approach, they say, adopted by U.S. airlines because of U.S. government pressure to hurry up and get their noise levels down.

Moreover, the Europeans contend that hush-kit planes are dirtier than normal in terms of exhaust pollution. Americans call that a bogus claim.

European officials have set a May 4 deadline for implementation of the global noise-abatement plan. Even without a plan in force, the value of older aircraft and hush kits has plummeted, out of concern that they won't be able to fly into and around Europe. Overall, the cost so far to the United States is about $2 billion, according to the industry.

The two sides have been talking about a solution, most recently at an aviation conference in Chicago last month, but to no avail. "We would like to settle this matter," Commerce Secretary William Daley said yesterday. "We can't settle this with a gun to our head, that in May they're going to pull the trigger on the regulations."

Europe has offered to postpone implementation past May, but Daley said the United States doesn't value that: "We should not be living in some situation where we're begging for some sort of temporary relief from a nuclear bomb being dropped on us? That's ridiculous."

A European Union spokesman said yesterday that the U.S. decision to go to the ICAO could result in Europe withdrawing offers to delay implementation. What Europe hopes to see is a United States truly committed "to working on real noise regulations under ICAO--so far we have not had such a commitment from the United States," the spokesman said.