Chinese president Xi Jinping has met former top diplomat Henry Kissinger, as the US pursues warmer ties with China.

Mr Kissinger’s surprise trip to the Chinese capital comes amid a flurry of visits by top US officials.

The former secretary of state, who is 100 years old, played a crucial role in helping China emerge from diplomatic isolation in the 1970s.

The US has stressed he is visiting in his capacity as a private citizen.

But given his outsized stature in China, he is likely acting as a backchannel for US-China negotiations, say experts.

Mr Kissinger was welcomed by Mr Xi at the Diaoyutai State Guesthouse, a more intimate space than the sprawling Great Hall of the People where official meetings with foreign diplomats are usually hosted.

A brief read-out did not give further details of their meeting, but lauded Mr Kissinger as a “legendary diplomat” and noted his previous achievements in brokering US rapprochement with China.

Mr Kissinger, who landed on Monday, also met top diplomat Wang Yi and defence minister Li Shangfu – who is under US sanctions – this week.

Chinese statements on the meetings have struck a conciliatory tone, with Mr Wang and Mr Li emphasising the need for respect, co-operation and “peaceful co-existence” between the two superpowers.

The read-outs also quoted Mr Kissinger as saying he was a “friend of China” and that “neither the United States nor China can afford to treat the other as an adversary”.

It is not known to what extent the US government was involved in Mr Kissinger’s trip. A State Department spokesman said earlier this week that they were aware of his visit, and that Chinese officials had also informed Secretary of State Antony Blinken when he visited Beijing in June.

Apart from Mr Blinken, Mr Kissinger is the only US figure Mr Xi has met in recent weeks – a measure of the respect the veteran diplomat still commands in China. Treasury Secretary Janet Yellen and US special envoy for climate John Kerry have also paid visits to Beijing, but did not get face time with China’s president.

Though Mr Kissinger has a controversial reputation in other parts of Asia for his role in the Vietnam War, in China, he remains highly regarded for helping the country emerge from diplomatic isolation.

In 1971, while the US and China officially had no diplomatic ties, Mr Kissinger had paid secret visits to Beijing to arrange a visit by then-US President Nixon.

The following year Mr Nixon landed on Chinese soil and met top leaders including Mao Zedong. It paved the way for the normalisation of US-China diplomatic relations and the opening-up of China to the world.

Since then, Mr Kissinger has been welcomed in China more than 100 times, Thursday’s read-out said.