U.S. and Japanese officials agreed to meet again this autumn about further deregulating commercial air travel over the Pacific, with the U.S. aiming for a tentative "open skies" treaty by year end.

One factor driving the talks: A push by Japan's All Nippon Airways Co. (ALNPY) to win approval of U.S. antitrust regulators.

Friday, negotiators concluded a round of talks in Washington aimed at expanding a 1952 agreement that liberalized air travel between the countries. The talks are focusing in part on traffic at Tokyo's two major airports, Narita and Haneda.

But serving as a backdrop is All Nippon's desire to fully operate within the Star Alliance of air carriers, negotiators said. The airline must first obtain antitrust immunity from the U.S. government, but U.S. policy limits antitrust exemptions to airlines from countries that have an "open skies" agreement with the U.S., said top U.S. negotiator John Byerly of the State Department.

"ANA has a very strong interest" in obtaining antitrust immunity, Byerly said. "That's led the Japanese government to be willing, as it has not been in the past, to consider 'open skies'."

Yoshiro Funabiki, counselor of transportation at the Japanese embassy in Washington, said All Nippon's interests are a factor in the "open skies" talks, but not "the sole and main motive."

Jean Saito, a U.S.-based spokeswoman for All Nippon, said she wasn't able to comment, and that officials from the company's Japan headquarters were unavailable.

Funabiki said Japan is serious about reaching an "open skies" agreement but that the country remains concerned about U.S. dominance in the trans-Pacific market. Those concerns are rising as Narita prepares to expand the number of flights there next year.

"The U.S. has too much dominance in market share across the Pacific ocean, and too much dominance especially in Narita," he said.

U.S. carriers currently operate a quarter of the flights coming in and out of Narita, Byerly said.

Under the current treaty between the U.S. and Japan, carriers that can fly between Narita and U.S. cities are: Delta Air Lines Inc. (DAL), UAL Corp.'s (UAUA) United Air Lines, and FedEx Corp. (FDX) in the U.S.; and Japan's two biggest airlines, Japan Airlines Corp. (JALSY) and All Nippon.

Byerly said the two sides this week "made progress in developing the outlines of a new agreement text," but added "there's still a good bit of work to do."

"We've decided in the U.S. government, now is the time to reach full liberalization" of air travel between the U.S. and Japan, Byerly said.

The two sides will hold another round of talks in Tokyo starting Oct. 26, Byerly said.

The U.S. is also in talks with the European Union on expanding an "open skies" pact that went into place in 2008. Those talks are scheduled to resume this autumn. Byerly said the U.S. aimed to have an updated agreement with the E.U. by the end of 2010.

U.S. Transportation Secretary Ray LaHood said at an international aviation summit in Washington this week that "open skies" agreements have benefited consumers and the airline industry, and that the Obama administration would work toward expanding them.

-By Josh Mitchell, Dow Jones Newswires; 202-862-6637; joshua.mitchell@dowjones.com

(Doug Cameron contributed to this article.)