RIYADH - Around 300 Chinese "decision makers" are attending Saudi Arabia's flagship investment conference this year, organisers said on Thursday, double last year's attendance as Riyadh deepens its relationship with China despite U.S. concerns.

Only around 15 people have cancelled their attendance of the annual Future Investment Initiative (FII), Richard Attias, CEO of the FII Institute said, as the war in Gaza spurred fears of a wider conflict that could affect the Gulf region.

"All the biggest and most important speakers are insisting on coming," Attias told reporters.

Wall Street financiers and Western investors have been the stars of the FII gathering since its launch by Crown Prince Mohammed bin Salman in 2017 to promote the kingdom's economic diversification plans.

But Riyadh's relationship with Washington frayed under President Joe Biden over several issues, including closer Saudi ties with China. In defiance of its key Western ally, Prince Mohammed invited Chinese President Xi Jinping to visit the kingdom and launched a Chinese-Arab summit.

The new wave of Chinese attendees comes in the wake of that summit, "an echo of the Chinese-Arab summit... There is a momentum,” Attias said.

In August, the BRICs group of nations, which includes China, invited Saudi Arabia to become a new member of the bloc.

Big Wall Street executives will still dominate the stages: JP Morgan CEO Jamie Dimon and Citi's Jane Fraser as well as senior global banking figures with a strong Asia presence like HSBC and Standard Chartered are all on the attendee list.

Korean President Yoon Suk Yeol, Kenyan President William Ruto and Rwandan President Paul Kagame will also attend the conference which is starting on Tuesday, Attias said.

Saudi Arabia is halfway through an ambitious economic transformation plan - Vision 2030 - to wean the economy off oil by creating new industries, generating jobs for citizens, and luring in foreign capital and talent.

But the kingdom has struggled to attract foreign investments to help it finance its mega-plans, leaving the government and its sovereign wealth fund, the PIF, shouldering the bulk of the spending.

As the conflict in Gaza adds uncertainty, Attias said the war and its impact on business will be a major topic in sessions during the conference.

(Reporting by Pesha Magid, editing by Aziz El Yaakoubi and Christina Fincher)