WASHINGTON, June 3 (AFP) - Central Intelligence Agency (CIA) Director William Burns made a secret trip to China last month hoping to shore up lines of communication with Beijing amid a deep chill in bilateral relations, a United States official said on Friday (Jun 2).

"Last month, Director Burns travelled to Beijing where he met with Chinese counterparts and emphasised the importance of maintaining open lines of communication in intelligence channels," the official said on grounds of anonymity.

The official provided no other specifics on the timing of the visit or who Burns met. The CIA as a policy does not discuss the director's travels.

But the visit came as Washington struggles to improve relations with China amid tensions over Taiwan's status, with both sides warning over the danger of a military conflict.

Washington has also accused China of considering supplying military goods to Russia in support of its invasion of Ukraine, which China denies.

Earlier this year US Secretary of State Antony Blinken cancelled a long-planned ice-breaker trip to Beijing after a Chinese surveillance balloon crossed the mainland United States, flying above sensitive military bases before it was shot down by a US fighter jet.

Blinken still hopes to go, State Department officials say, when conditions improve.

Earlier on Friday, US Defense Secretary Lloyd Austin and his Chinese counterpart Li Shangfu spoke briefly at the Shangri-La Dialogue security forum in Singapore, after many months in which the two sides' militaries had not communicated directly at a senior level.

Their short conversation came after Beijing had declined the Pentagon's invitation for a formal meeting in Singapore.

The United States has also infuriated Beijing by restricting US exports to China of advanced microchips, chip technologies and manufacturing equipment, pressing allies to side with Washington.

And Washington has faulted China for not doing enough to halt exports of chemicals that are turned into deadly fentanyl in Mexico and sold in the United States.

China, for its part, has put pressures and limitations on some US businesses operating in the country, underscoring the competition between the world's two largest economies.

At the Group of Seven (G7) meeting in Japan last month, US President Joe Biden predicted that ties between Washington and Beijing would soon thaw, after the February balloon incident.

After that, "everything changed in terms of talking to one another. I think you're going to see that begin to thaw very shortly", Biden said in Hiroshima.

On Friday, White House national security adviser Jake Sullivan made a separate overture to Beijing, saying that it should be part of nuclear arms pacts between the United States and Russia owing to the rapid build-up of its nuclear warhead supply.

In terms of trying to agree on limitations, the US is "ready to engage China without preconditions", said Sullivan.