HONG KONG • The Chinese government, which has long used its vast market as leverage over United States technology firms, is now asking some of those firms to directly pledge their commitment to contentious policies that could require them to turn user data and intellectual property over to the government.

Beijing distributed a document to some US tech companies earlier this year, in which it asked them to promise they would not harm China's national security and would store Chinese user data within the country, according to three people with knowledge of the letter.

The letter also asks the US companies to ensure their products are "secure and controllable", a catchphrase that industry groups said could be used to force them to build so-called back doors that allow third-party access to systems, provide encryption keys or even hand over source code.

The document was sent by the China Internet Security Certification Centre, according to one of the people with knowledge of the letter. It is unclear when Chinese officials want a response from the firms.

Next week, Beijing has also planned a tech forum in Seattle between Chinese Internet czar Lu Wei and tech companies including Apple, Facebook, IBM, Google and Uber, in a show of how it can get some of the world's leading tech players to meet. It is timed to coincide with President Xi Jinping's first state visit to the US.

The situation is tricky for the companies. Signing the pledge could set a precedent of US tech firms openly cooperating with Beijing. But a refusal could bring fresh restrictions or penalties in China's market.

"Everyone has assumed that it is easier in the market if you are seen as a friend of China," said Dr Adam Segal, a senior fellow at the Council on Foreign Relations.

NEW YORK TIMES