US Vice-President Joe Biden expressed his country's misgivings about China's air defence identification zone (ADIZ) in lengthy talks with President Xi Jinping in Beijing yesterday.
A senior US official said: "The vice-president laid out our position in detail. He indicated that we don't recognise the zone, that we have deep concerns."
He added that Biden told Xi that "we are looking to China to take steps to reduce tensions".
"President Xi was equally clear in laying out their view of the zone and of territorial disputes in the region," the official said. "Ultimately, President Xi took on board what the vice-president said. It's up to China, and we'll see how things will unfold in the coming days and weeks."
Xi called for closer co-operation and dialogue with America, while Biden said the bilateral relationship had to be built on trust.
The declaration late last month of the zone over the East China Sea drew criticism from the US and China's Asian neighbours. It includes the airspace above disputed islands known as the Diaoyus in Chinese and the Senkakus in Japanese.
A Xinhua report said Xi reiterated China's view on the zone.
The other major topic of discussion was North Korea.
"They talked at some length about what the Iran example means for North Korea," the US official said, citing the combination of pressure and unity of partners that helped bring about an interim nuclear deal last month limiting Iran's programme.
After the meeting, which was due to last 45 minutes but ran to two hours, Xi reiterated to Biden that China was ready to work with the US to build a new model of major-country relations and respect each other's core interests. Beijing has occasionally included sovereign issues over the South and East China seas as part of those core interests.
Citing climate change and energy security, Xi said "the world as a whole is not tranquil".
"To strengthen co-operation and dialogue is the only right choice facing both our countries," Xi said.
In response, Biden said the new model of major country co-operation had to be built on trust and "a positive notion about the motives of one another".
"As you have pointed out, Mr President, complex relationships require sustained high-level engagement and that's why I am here. This is a hugely consequential bilateral relationship that is going to play a significant part in affecting the course of the 21st century," Biden said.
Washington has criticised Beijing for unilaterally establishing the air defence zone without prior consultation. It also said Chinese rules for the zone do not conform to international norms. Beijing insists it has the right to set up the zone, as a means of self-defence, in the way that neighbours including Japan and South Korea have already established such zones.
In Tokyo on Tuesday, Biden sought to reassure Japan by publicly expressing concerns about the zone and stressing the importance of the US-Japan alliance for stability in the region.
However, despite Japan's hope that the US would join its call for China to rescind the zone, Biden did not make any such demand. He urged both Tokyo and Beijing to have a crisis communication mechanism. Japanese leader Shinzo Abe also avoided making such a call in his joint appearance with Biden in Tokyo.