The four main political parties have threatened to reject an air transport accord between Switzerland and Germany aimed at ending a long running dispute over noise pollution out of Switzerland's main Zurich-Kloten airport.

A spokesman for the four governing parties said the result of the negotiations between Switzerland and neighbouring Germany last month was unacceptable. He made the statement following talks between the parties and the cabinet in Bern on Friday.

In April the Swiss transport minister, Moritz Leuenberger, agreed to cut to less than 100,000 per year the number of flights using German airspace before landing at Zurich-Kloten airport. This reduces the current level of flights by more than a third.

The measure is due to take effect by 2005. It also includes extending a night time flight ban and a reduction in the number of flights on weekends. But parliament still has to debate the treaty.

Communes in southern Germany, on the border with Switzerland, have been complaining about noise pollution from aircraft flying over their territory.

The main Swiss parties on Friday called on the cabinet to review the accord with Germany. They said there were doubts whether the agreement was in line with international regulations.

The parties also asked the government to ensure that Switzerland's main airport does not suffer any discrimination and lose its competitiveness with airports in Germany.

A government spokesman said the transport ministry agreed to carry out further inquiries into legal aspects of the treaty.

swissinfo with agencies

In compliance with the JTI standards

More: SWI swissinfo.ch certified by the Journalism Trust Initiative