White House national security adviser Jake Sullivan met Chinese Foreign Minister Wang Yi in Malta for hours this weekend, Beijing and Washington said on Sunday, as the world’s two largest economies seek to stabilise troubled relations.

Both sides held “candid, substantive and constructive” talks during multiple meetings held September 16-17, according to separate statements from the White House and the Chinese foreign ministry published on Sunday.

There were also “limited” early signs that severed military communications between the two sides may start to be restored, a senior Biden administration official said.

Chinese officials did not comment on the prospect of military-to-military communication.

Sullivan’s meeting with Wang was the latest in a series of high-level discussions between US and Chinese officials that could lay the groundwork for a meeting between US President Joe Biden and Chinese President Xi Jinping later this year.

They come amid a string of upheavals in the Chinese government’s top ranks, including the disappearance of defense minister Li Shangfu, and wobbles in the country’s economy that have caused consternation in foreign capitals.

The Malta talks spanned about 12 hours over the two days, a senior Biden administration official told reporters. Sullivan last met Wang in Vienna in May.

China’s foreign ministry said both sides agreed to maintain high-level exchanges and hold bilateral consultations on Asia-Pacific affairs, maritime affairs and foreign policy.

The United States told China it was ready to work together on counter-narcotics, artificial intelligence and climate change even as it expressed concerns over unspecified Chinese support for Russia and Beijing recently sending fighter jets across the sensitive median line of the Taiwan Strait, the US official said.

Wang cautioned the United States that the Taiwan issue is the “first insurmountable red line of Sino-US relations,” according to the Chinese foreign ministry statement. China claims the self-ruled island as its own territory.

Wang also said China’s development has a “strong internal momentum” and “cannot be stopped”, and that the “Chinese people’s legitimate right to development cannot be deprived”.

United States has said it sought a healthy competition with China based on fair rules that benefit both countries, but China said despite inviting competition, the US has been engaging in suppression and containment of its growth.

The US official said “there have been some small or limited indications” that Beijing is ready to re-open some cross-military communications used to de-escalate conflict between the two countries after those ties were cut following an August 2022 visit by former US House of Representatives Speaker Nancy Pelosi to Taiwan that enraged China.

In its statement, the White House strongly suggested that more meetings are to come between the US and China, adding that both sides “committed to maintain this strategic channel of communication and to pursue additional high-level engagement and consultations in key areas … in the coming months.”

Biden this month expressed disappointment that Xi skipped a summit of Group of 20 leaders in India, but said he would “get to see him.” The next likely opportunity for Biden to hold talks with Xi is an Asia-Pacific Economic Cooperation summit in San Francisco in November, where US aides for months have hoped to stage such a meeting.

US Commerce Secretary Gina Raimondo, Secretary of State Antony Blinken, Treasury Secretary Janet Yellen and Biden climate envoy John Kerry have traveled to China this year to thaw relations and ensure continued communication between the two countries amid tensions that flared after the US military shot down a Chinese surveillance balloon that traveled over the United States.

Biden and Xi last met in 2022 on the sidelines of a G20 summit on Indonesia’s resort island of Bali.