RAS AL KHAIMAH, United Arab Emirates (Reuters) - Weakening investor interest in clean energy is due to elusive targets, high costs and lack of financing, according to Igor Sechin, boss of Russia's biggest oil producer Rosneft and a well-known green energy sceptic.

Russia, a leading producer of oil and natural gas, and China have set goals to reach carbon neutrality by 2060, 10 years later than most of the developed world.

Russian President Vladimir Putin has criticised the green movement in Europe for capitalising on peoples' fears about climate change, while questioning Germany's commitment to phasing out coal.

Sechin has been sceptical about the green agenda, saying the human contribution to the climate change has been overestimated.

"Over the past three years, Western stock markets' enthusiasm for the renewable energy sector has largely faded. Shares of companies producing clean fuels have fallen several times over two years," Sechin told a conference in the United Arab Emirates.

"The reasons for this attitude of investors are the inability of green economy companies to achieve their goals on time, including due to rising costs, delays in the issuance of government loans and the lack of availability of new financing."

He cited global energy majors, such as Chevron Shell and BP, which he said had "suspended alternative fuel production projects".

"In particular, I am pleased to see the move away from producing aviation fuel from used cooking oil," Sechin said with a wry smile.

International oil majors have slowed investments in renewables and low-carbon business as they face investor pressure to boost returns and maintain large shareholder payouts amid surging costs, supply chain issues and technical problems.

(Reporting by Olesya Astakhova and Yousef Saba. Writing by Vladimir Soldatkin. Editing by Mark Potter)

By Olesya Astakhova and Yousef Saba