As U.S. superhero movie "Avengers: Age of Ultron" earns record-breaking sums at the Chinese box office, a more low-key film playing in cinemas sheds light on a political milestone that helped open China's doors to such cultural imports.

"That we can watch 'Avengers' in cinemas today is precisely because of Deng Xiaoping's U.S. visit in 1979," said Fu Hongxing, referring to his "Mr. Deng Goes to Washington", a documentary which opened on Friday.

Fu said Deng's nine-day trip, between Jan. 28 and Feb. 5 1979, changed the fate of the Chinese people and even the global geopolitical situation, but that "it has never been given a good elucidation".

Deng was the first Chinese leader to visit the United States after the two countries established diplomatic relations in January 1979. The then vice premier met American politicians, received interviews, visited Ford's assembly plant and NASA's Johnson Space Center.

The trip demonstrated China's resolve to open to the world and learn from developed countries in science and technology, education and culture.

To make the movie, Fu trawled through archives, purchased video footage from U.S. TV networks at a cost of 250 U.S. dollars per second, and acquired the support of Deng's family.

Key figures interviewed in the film include former U.S. President Jimmy Carter, former U.S. National Security Advisor Zbigniew Brzezinski, Deng's bodyguards and secret service agents from the White House.

Retired Chinese basketball player Yao Ming also appears, explaining how he feels about Deng's influence.

Though Fu had success in the 1990s with "Zhou Enlai's Diplomatic Career", a documentary on former Premier Zhou Enlai, he encountered difficulty securing funding and official approval for "Mr. Deng Goes to Washington", which includes controversial cartoon images of Deng. Cartoons of Chinese leaders are largely disapproved of in China.

Lyu Muzi, Fu's wife and the film's executive producer, said it is not a government-backed project and they did not even try to apply for papers to guarantee favorable screening arrangements at theaters.

After turning down some investment for fear of money "with dubious background", Lyu remortgaged their house to get money for the production.

Fu said the cartoons were used "to better reflect Deng's character" and that he hopes the film can give viewers a more objective view of history.