The US and China have had "very direct" talks about concerns over China's new air defence identification zone, US Vice-President Joe Biden said.
Speaking after meetings with Chinese leader Xi Jinping, Mr Biden said the zone had caused "apprehension" in Asia.
Talks in Mr Biden's Asia trip have been dominated by a new air zone declared by China, which covers islands controlled by Japan in the East China Sea.
China says its move is consistent with "international law and practice".
China announced a new Air Defence Identification Zone (ADIZ) last month, and said aircraft flying through the zone must follow its rules, including filing flight plans.
The ADIZ covers islands claimed and controlled by Japan, and a submerged rock claimed by South Korea.
The US, Japan and South Korea have rejected China's zone, and flown undeclared military aircraft through the ADIZ.
'World not tranquil'
Mr Xi and Mr Biden met for around five hours on Wednesday.
Neither mentioned the air zone dispute when they spoke to reporters after the talks.
However, Mr Biden told US businessmen on Thursday: "I was very direct about our firm position and our expectations in my conversations with President Xi."
China's declaration of the new zone had "caused significant apprehension in the region," he said, adding that China had "increasing responsibility to contribute positively to peace and security".
Meanwhile, Chinese Foreign Ministry spokesman Hong Lei said: "During the talks the Chinese side repeated its principled position, stressing that the Chinese move accorded with international law and practice."
"The US side ought to take an objective and fair attitude and respect [China's move]," Mr Hong added.
Speaking to reporters on Wednesday, Mr Xi had said that "profound and complex changes" were under way in Asia, and "the world, as a whole, is not tranquil".
"Enhancing dialogue and co-operation" was the "only correct choice" for the US and China, Mr Xi added.
A senior White House official, speaking on condition of anonymity, said Mr Xi and Mr Biden also spent "a substantial amount of time" discussing North Korea, including the country's internal situation and ways to push Pyongyang towards denuclearisation.
In his speech to US businessmen, Mr Biden also said that the two sides had "profound disagreements" over the treatment of US journalists in China.
"Innovation will thrive where people breathe freely, speak freely, are able to challenge orthodoxy, where newspapers can report the truth without fear of consequences," he said.
Earlier this week, a reporter from Bloomberg was denied access to a media event attended by UK Prime Minister David Cameron and Chinese Premier Li Keqiang.
The websites of Bloomberg and the New York Times have been blocked in China after they reported on the alleged wealth of the families of Mr Xi and former Premier Wen Jiabao.
Foreign ministry spokesman Hong Lei said at a press briefing on Thursday that China "provided an extremely convenient atmosphere for foreign reporters reporting in China".
He added that China managed foreign journalists in accordance with its law.
Both Bloomberg and the New York Times have not received new journalist visas for more than a year, the BBC's Martin Patience in Beijing reports.
Foreign journalists working in China are frequently denied access to government officials, are often barred from sensitive areas of the country and have on occasions been attacked by government-hired thugs while reporting stories, our correspondent adds.
Mr Biden will fly to South Korea later on Thursday.
Earlier this week, he met Japanese President Shinzo Abe in Tokyo, where he reaffirmed the US' alliance with Japan.