BEIJING (Reuters) - Chinese airlines are likely to purchase planes worth $1.025 trillion over 20 years as they expand fleets to cater to robust growth in domestic and overseas tourism, Boeing Co <BA.N> said in a more bullish forecast of Chinese aviation demand.

Saying China as a market continued to exceed expectations, Boeing estimated 6,810 aircraft purchases in the period to 2035, up 7.6 percent from its previous prediction of demand until 2034.

"The continuing expansion of China's middle class, coupled with new visa policies and a wide range of widebody airplanes... gives us every reason to expect a very bright future for China's long-haul market," Randy Tinseth, Boeing Commercial Airplanes' vice president of marketing, said in a statement.

He also said that he expects passenger traffic to grow 6.4 percent in China annually over the next 20 years.

Boeing has stayed bullish on China even as other U.S. companies have expressed concern over the country's slower economic growth. A senior Boeing executive said in August that the plane maker was not seeing any softness in demand in China.

Boeing and European rival Airbus <AIR.PA> have been jostling for market share in China, the world's fastest growing aviation market, with both opening assembly plants in the country.

Boeing said more than 50 percent of commercial jetliners operating in China are its planes.

China, however, is also striving to develop its own aircraft manufacturing capability and aims for its long-delayed C919 jet to make its maiden flight by the end of the year. It hopes the C919 will compete with Boeing's 737 and Airbus's A320.

(Reporting by Beijing Newsroom and Brenda Goh; Editing by Edwina Gibbs)