If US Airways can persuade federal regulators and outhustle its competitors, nonstop airline flights between Philadelphia International Airport and China could start as early as next year, airline and government officials say.

US Airways has joined four other major airlines in expressing interest to the U.S. Department of Transportation in serving the next available U.S.-to-China route, which the federal agency expects to award later this year so service can start March 25, 2008, department spokesman Bill Mosley said yesterday.

US Airways has not decided yet which of its connecting hubs - Philadelphia; Charlotte, N.C.; or Phoenix - it will seek to connect to China when it makes an application to the government, airline spokesman Philip Gee said.

But, Gee noted, Philadelphia is the largest U.S. metropolitan area that has no nonstop air service to China, one of the world's fastest-growing economies.

Whichever city is chosen, US Airways would face fierce competition from the other airlines, supported by their hub cities. U.S.-to-China air routes are among the most sought-after in the world because service between the countries now is limited and traffic is strong, with flights heavily used by business travelers willing to pay high fares.

Tempe, Ariz.- based US Airways Group Inc. also would have to buy or lease airplanes to fly to China. The Airbus A330, the largest jet in its fleet, does not have the range to go nonstop from any of the hubs, Gee said. China's capital, Beijing, is about 6,900 miles by air from Philadelphia, 6,500 miles from Phoenix, and 7,100 from Charlotte.

US Airways has not discussed its interest in a China route with Philadelphia airport managers, airport spokesman Mark Pesce said yesterday.

Mjenzi Traylor, the first deputy city commerce director, said that studies done for the Greater Philadelphia Global Partnership, a business-development group, have determined that there was strong demand for charter airline flights between Philadelphia and China. That work could serve as a basis to measure demand for scheduled flights, which would have city support, he said.

Philadelphia currently has 52 daily nonstop international flights to 31 destinations, the great majority of them operated by US Airways. The airport has a total of about 700 daily departures to more than 120 cities.

American Airlines, Continental Airlines, Delta Air Lines and Hawaiian Airlines also are expected to seek the coveted service, which could be to any of China's largest cities, federal officials said.

Delta has applied to fly between Atlanta, its largest hub, and Shanghai, Mosley said. The other carriers, including US Airways, have not made formal applications and have not said which of their hubs they would use, he said.

International airline routes, unlike domestic ones, are governed by treaties between nations that can limit the number of weekly flights airlines can operate. The United States has so-called "open skies" agreements with dozens of countries, including Canada, Mexico, and most European nations, that allow unlimited flights, but China is not among them.

Under a six-year agreement with China signed in 2004, U.S. airlines will be able to offer a total of 195 new flights a week. The new flights will be phased in over the term of the pact.

Last week, the Transportation Department ended a spirited competition among carriers by awarding United Airlines the right to start nonstop flights - seven round-trips a week - between Washington Dulles Airport, where it has a hub, and Beijing. United is scheduled to start the service March 28.

Contact staff writer Tom Belden at 215-854-2454 or tbelden@phillynews.com.