U.S. officials say Vice President Joe Biden expressed Washington's concerns over China's new air defense identification zone, or ADIZ, during talks with President Xi Jinping in Beijing Wednesday.
The officials, who did not want to be named, told reporters the vice president indicated the U.S. does not recognize the zone and is looking to China to take steps to reduce tensions.
The U.S. officials say President Xi was equally clear in laying out the Chinese view of the zone and of territorial disputes in the region.
U.S. officials say that in addition to the air defense zone, the two also held broad bilateral discussions on topics ranging from economic reforms to North Korea, which is also expected to be on Biden's agenda when he travels to South Korea on Thursday.
The visit to Beijing comes one day after a visit to U.S. ally Japan, where Biden said he was "deeply concerned" at China's ADIZ in the East China Sea.
After meeting Japanese Prime Minister Shinzo Abe, Biden suggested establishing "confidence building measures, including emergency communications channels" to help reduce tensions.
Joseph Cheng, a political science professor at the City University of Hong Kong, tells VOA that such measures could be welcomed by both sides.
"Some kind of hotline is definitely possible. I think all parties concerned welcome this. And further discussions on confidence building measures are to be welcomed. Ideally, there should be some sort of code of conduct along the lines of that concluded between China and ASEAN."
But Cheng does not expect Biden to take on a formal mediating role, since China has been reluctant to involve outside powers in what it views as bilateral territorial disputes.
Further dialogue could also be complicated by Japan's refusal to formally recognize a dispute over the islands, something it views as a weakening of its position.
Bonnie Glaser, a China expert at the Washington-based Center for Strategic and International Studies, tells VOA that Biden finds himself in a tough position.
"It is quite difficult for Vice President Biden in this particular heightened, tense atmosphere, to try and urge the two sides to resume political dialogue and particularly to talk about confidence building measures between the two militaries."
China late last month set up its Air Defense Identification Zone. Beijing has requested that all airplanes submit flight plans ahead of flying through the zone.
The U.S. has repeatedly rejected the Chinese zone. Last week, it flew two unarmed B-52 bombers on "routine" training missions through the area, ignoring Chinese demands the aircraft identify themselves.
While Beijing said it monitored the B-52 flights, it did not interfere. Later, however, it did scramble fighter jets to the area, heightening concerns about a possible miscalculation in the air.
Ahead of Biden's arrival, China's Defense Ministry said its determination to defend the zone is "unwavering, and the military is fully capable of exercising effective control" over the area.
The state-controlled China Daily newspaper also warned in an editorial Wednesday that Biden should not expect any substantial progress if he comes (to China) simply to, in its words, "repeat his government's previous erroneous and one-sided remarks."