The United States and China have agreed in principle for their presidents to hold a virtual meeting before the end of the year, a senior U.S. administration official said on Wednesday, after high-level talks aimed at improving communication between the two countries.

The closed-door meeting at an airport hotel in the Swiss city of Zurich between U.S. national security adviser Jake Sullivan and China's top diplomat Yang Jiechi was their first face-to-face encounter since an unusually public and acrid airing of grievances in Alaska in March.

U.S. officials had suggested that the meeting was a follow-on from President Joe Biden's Sept. 9 call with Chinese President Xi Jinping, prior to which the world's top two economies appeared to have been locked in a stalemate.

The White House said Sullivan raised concerns about contentious issues such as China's actions in the South China Sea, as well as on human rights and Beijing's stances on Hong Kong, Xinjiang, and Taiwan.

At the end of the day, however, both Beijing and Washington said the talks, which lasted six hours, were constructive and candid. The U.S. side said the tone was very different from Alaska.

"We do have out of today's conversation an agreement in principle to hold a virtual bilateral (summit) meeting before the end of the year," the U.S. official told reporters.

Asked for further details, White House spokeswoman Jen Psaki said: "We're still working through what that would look like, when and of course the final details we don't quite have them yet."

Early speculation had been that the two might meet in person at the G20 summit in Italy in October, but Xi has not left China since the outbreak of the pandemic early last year.

"Today's conversation, broadly speaking, was a more meaningful and substantive engagement than we've had to date below the leader level," the official said, adding that Washington hoped it would be a "model for future encounters."

The official said it shouldn't be seen as a thaw in relations, however.

"What we are trying to achieve is a steady state between the United States and China where we are able to compete intensely but to manage that competition responsibly," the official said.

China's Foreign Ministry said in a statement that Yang told Sullivan that confrontation would damage both countries and the world.

"The two sides agreed to take action ... to strengthen strategic communication, properly manage differences, avoid conflict and confrontation," the ministry statement said.

TAIWAN TENSIONS

Biden's call with Xi in September ended a nearly seven-month gap in direct communication between the leaders, and the two discussed the need to ensure that their competition does not veer into conflict.

Biden said on Tuesday that he spoke to Xi about Taiwan and they agreed to abide by the "Taiwan agreement", as tensions ratchet up between Taipei and Beijing.

Taiwan has reported 148 Chinese air force planes in the southern and southwestern part of its air defence zone over a four-day period beginning on Friday, the same day China marked a patriotic holiday, National Day. 

Taiwan's Foreign Ministry, which had sought clarification from the United States about Biden's comments, said on Wednesday that Washington reassured them that its approach to Taiwan had not changed, and that its commitment to the democratically governed island claimed by Beijing was "rock solid". 

In his comments on Tuesday, Biden appeared to be referring to Washington's long-standing policy under which it officially recognizes Beijing rather than Taipei, and the Taiwan Relations Act, which makes clear that the U.S. decision to establish diplomatic ties with Beijing instead of Taiwan rests upon the expectation that the future of Taiwan will be determined by peaceful means.

The White House said Sullivan will also visit Brussels for meetings with NATO and European Union officials, as well as Paris, and will brief the Europeans on his meeting with Yang.

With trade tensions also at the top of the U.S.-China agenda, U.S. Trade Representative Katherine Tai, in Paris for Organisation for Economic Co-operation and Development meetings, has said she hopes to hold discussions soon with Chinese counterparts.

On Monday, Tai unveiled the results of a months-long "top-to-bottom" review of China trade policy, pledging to hold "frank" talks with Beijing about its failure to keep promises made in former President Donald Trump's trade deal and end harmful industrial policies.