The US government tentatively selected United Airlines to provide new nonstop service to China, regulators and the airline said on Tuesday.

The US Transportation Department awarded United daily service between Washington's Dulles Airport and Beijing's China Peking Capital Airport. Flights will begin March 25 if the agency's decision becomes final.

In winning the route, United beat competing applications from American Airlines, Continental Airlines and Northwest Airlines, which all want to bolster their existing China service.

The Transportation Department said United's proposed capital-to-capital route benefits the greatest number of travelers.

"The new route closes a critical service gap, connecting the capital of the United States, the largest economy in the world, with the capital of China, the fastest-growing economy in the world," said UAL Chief Executive Glenn Tilton in a statement.

US carriers, battered by low-cost competition at home, have sought out growth on lucrative international routes, and China's economic expansion presents a strong opportunity for airlines with service there.

The United States keeps tight reins on rights to fly to China, so competition for the routes among airlines is stiff.

Interested parties have 14 days to object to the government decision. The Transportation Department then has seven days to answer the objections. After that, the department will review the comments and issue a final decision.

American, Continental and Northwest each expressed disappointment that their applications weren't accepted. But none indicated plans to formally object to the decision.

"The record showed that Northwest's proposal would have benefited the most passengers, served the most US cities, and provided the quickest and most efficient routings to China," said Northwest spokesman Bill Mellon in a statement.

Northwest had proposed flying from Detroit to Shanghai. The carrier hopes to renew its application if other routes become available, Mellon said.

Michael Whitaker, United Airlines vice president for regulatory affairs and alliances, told CNBC in an interview the carrier would fly the route with Boeing 747 aircraft.

He noted that other United flights to China run nearly full on a yearly basis and expected the same for the new Beijing route. United currently has four nonstop flights to China.