SHANGHAI (Reuters) - Chinese electric vehicle (EV) maker Nio's founder called for openness in a rare speech in the United States, where politicians have been seeking to further restrict China's access to the world's second-largest auto market.

William Li, speaking at an event at Harvard University on Saturday, said rapid EV growth in China resulted from an "open and competitive" market where "all products are welcome regardless of their brands or origins".

He cited Tesla's success in China, where billionaire Elon Musk's automaker has sold 1.36 million EVs in the past three years, adding its presence boosted EV penetration and energised the industry.

"Competition will lead to greater investment, longer time to break even, less margin for mistakes and lower chances of success," Li said, according to a transcript of his speech provided by the company.

"However, we do not expect China to adopt policies to protect domestic players because we also see the other side of the coin, where openness will ultimately benefit industries and sustainability, and make the best companies even better."

Tensions are rising between China and the West over Chinese EV exports, which Washington and Brussels say are heavily subsidised by the state and could harm domestic automakers.

A European Union is investigating Chinese EV makers such as BYD, Geely and SAIC could lead to tariffs over the subsidies.

Few Chinese-made EVs are sold in the U.S. market, where they already face steep tariffs. China's biggest EV maker, BYD, said it had no plans to sell its cars into the country.

President Joe Biden, a Democrat, is considering raising tariffs on Chinese EVs, auto executives have told Reuters. Republican Senator Marco Rubio and Democratic Senator Sherrod Brown have highlighted concerns over cheap Chinese EVs, including on national security grounds.

Li has said Nio was studying the feasibility of selling into the U.S. on a quarterly basis. In the Chinese market, with a lineup priced from 298,000 yuan ($42,000) for the premium segment, the automaker sold 30,053 EVs in the first three months, compared to 132,420 vehicles sold by Tesla.

($1 = 7.2371 Chinese yuan renminbi)