WASHINGTON - Four US airlines have made their final arguments in a dogfight over the lucrative rights for a route to China that will be awarded by the US government by the end of 2006.

The US and Chinese governments each will be awarding rights to a local carrier for seven flights a week connecting the two countries, under a 2004 aviation agreement, US Transportation Department spokesman Bill Mosley said.

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The four US carriers -- American, United, Continental and Northwest -- have been rallying support in an effort to win the rights to the fast-growing China market, and filed final comments with US authorities Tuesday.

The carriers have been launching websites, getting signatures on petitions and drawing support from elected officials. Continental even handed out fortune cookies in Washington in support of its bid.

"We continue to get letters of support from members of Congress, state houses and citizens throughout the United States in support of our bid," said Mary Frances Fagan of American Airlines, which is proposing a route linking Dallas-Fort Worth, Texas, and Beijing.

Fagan said the American proposal would serve a larger population base than a competing offer from United to link Washington and Beijing.

Additionally, she said selecting American would "provide much-needed competitive balance," because Northwest and United already have more flights to China.

As a result of this, Fagan said, "The choice is between American and Continental," which each have only one flight daily to China.

The other carriers however are equally adamant that they offer the most advantages.

United's proposal is backed by a coalition of former senior government officials and business groups, claiming it would bring the first nonstop service linking the two capitals.

Jane Garvey, a former Federal Aviation Administration chief who is co-chair of the Capital-to-Capital Coalition, stated, "United's proposal offers not only the largest number of seats, it is clearly the proposal that offers the greatest benefit to the critical relationship between the US and China."

Northwest spokesman Dean Breest said the carrier's proposed Detroit-Shanghai service has garnered the most public support with more than 170,000 people having signed petitions for the route.

"Based on the evidence of record, it is clear that the selection of Northwest for Detroit-Shanghai nonstop service will establish the largest and most effective hub gateway to China -- creating the most significant benefits for US-China passengers throughout the entire eastern United States," Northwest said in its filing with the Department.

Additionally, Breest said the Northwest plan would serve more passengers -- some 214,000 in the first year -- and have the shortest nonstop flight to China over a polar air route.

"The Detroit-Shanghai proposal maximizes the public benefits," he said.

Continental argues that its bid for a route linking Newark, New Jersey -- just outside New York -- and Shanghai is superior and has wide support from business groups.

Continental spokeswoman Mary Clark said the proposal -- which would include a leg from Cleveland to Newark -- makes the most sense because it would serve the most populous area.

"It's five times that of Dallas, twice that of Detroit and 50 percent larger than Washington," Clark said.

She added that United "already has routes to China" and could move one of its flights to Washington (from Chicago or San Francisco) "if they really wanted to."

The stakes are high with US-China economic ties accelerating.

An American Express business travel survey found corporations in China spent US$7.41 billion on air travel in 2005, making China the fourth-biggest business travel market in the world.

Although most observers expect a single carrier to win the rights, Mosley said it is possible the seven weekly flights could be divided among two or more airlines.

The spokesman said he expects a DOT decision "as soon as possible" after the proposals are analyzed. Service would start in March 2007.