The United States and the European Union are unlikely to negotiate a settlement to a dispute over subsidies for aircraft rivals Boeing and Airbus, U.S. trade officials told reporters on Friday. The dispute is potentially the biggest ever to go before the World Trade Organization. Each side accuses the other of showering billions of dollars on their aerospace giant, according to Reuters. While Washington remains open to a negotiated settlement, "we haven't made the progress we've been looking for, which is why we've been pushing forward with the WTO case." a U.S. trade official said during a telephone briefing on the U.S. Trade Representative's annual foreign trade barriers report. Jim Mendenhall, general counsel in the U.S. Trade Representative's office, started the phone call with a set of on-the-record remarks. But several other U.S. trade officials who spoke during the briefing did so on the condition they not be individually identified. The United States and the EU filed tit-for-tat cases at the World Trade Organization over government support for Boeing and Airbus in May 2005. Since then, both sides have professed their desire for a negotiated settlement without any notable movement toward that. --More 23 11 Local Time 20 11 GMT