Assad is on his first official trip to China in almost two decades as he seeks financial support to rebuild his devastated country, as well as rehabilitation for his regime from years of isolation over Syria's civil war.

He will attend the opening ceremony of the 19th Asian Games in Hangzhou on Saturday.

Xi and Assad met in the eastern Chinese city on Friday afternoon, state media said.

"Today, we will jointly announce the establishment of the China-Syria strategic partnership, which will become an important milestone in the history of bilateral relations," Xi told Assad, according to a readout from state broadcaster CCTV.

"Faced with an international situation full of instability and uncertainty, China is willing to continue to work together with Syria, firmly support each other, promote friendly cooperation, and jointly defend international fairness and justice," he added.

Relations between the two countries "have withstood the test of international changes", Xi said.

"And the friendship between the two countries has been strengthened over time," he added.

The leaders were each flanked by nine aides at a large rectangular wooden table, a CCTV video clip showed, as two flags from each country were set in front of a Chinese painting in the meeting room.

- 'New level' -

China is one of only a handful of countries outside the Middle East that Assad has visited since the 2011 start of a civil war that has killed more than half a million people, displaced millions more, and battered Syria's infrastructure and industry.

China's foreign ministry has said his visit will take ties to a "new level".

"China and Syria have a traditional and deep friendship," foreign ministry spokesperson Mao Ning told a regular briefing.

"We believe that President Bashar Al-Assad's visit will further deepen mutual political trust and cooperation in various fields between the two countries," she added.

Assad's visit is his first to China since 2004.

Analysts expect Assad's visit to China will focus, in part, on funds for reconstruction.

It also comes as China's influence in the Middle East grows.

This year Beijing brokered a deal that saw longtime regional rivals Saudi Arabia and Damascus-backer Iran agree to restore ties and reopen their respective embassies.

The detente was followed by Syria's return to the Arab fold at a summit in Saudi Arabia in May, ending more than a decade of regional isolation.