The Foreign Ministry on Thursday called for a "level and stable" playing field for Chinese companies in overseas business after a report that a White House-ordered review had found no clear evidence of Huawei spying for China.

But Chinese experts said Washington's reasoning that the telecoms equipment firm is still dangerous for the US and "has the capability" to attack is a typical "presumption of guilt".

The US will lose through such thinking, the experts said, adding that Chinese companies going abroad must consider the political risks.

Huawei is among a slew of Chinese enterprises fighting for their rights in the United States market.

Also on Thursday, China's largest machinery maker Sany Group said it will "fight to the very end" in its lawsuit against US President Barack Obama, after the president blocked a wind farm project citing national security concerns.

Reuters cited people familiar with the 18-month review on Huawei as saying that intelligence agencies and other departments conducted the largely classified inquiry, delving into reports of suspicious activity and asking detailed questions of nearly 1,000 telecoms equipment buyers.

"We knew certain parts of government really wanted" evidence of active spying, said one of the people, who requested anonymity. "We would have found it if it were there."

Instead, people leading the review concluded early this year that relying on Huawei, the world's second-largest maker of networking gear, was risky for other reasons, such as the presence of "vulnerabilities" that hackers could exploit.

But the Reuters report said it is unclear if security vulnerabilities found in Huawei equipment were placed there deliberately.

At a conference in Kuala Lumpur last week, Felix Lindner, a leading expert in network equipment security, said he had discovered a series of vulnerabilities in Huawei's routers, Reuters reported.

Lindner, who spent months investigating Huawei code, said the vulnerabilities appeared to be the result of sloppy coding and poor procedures, rather than any deliberate attempt at espionage.

The US House of Representatives Intelligence Committee last week issued a report warning that two leading Chinese technology companies, Huawei and ZTE, pose possible threats to US national security, without presenting concrete evidence.

The committee also criticized Huawei's leadership for failing to provide details about its relationships with the Chinese government.

Huawei has rejected the House report as unfair and inaccurate, while ZTE said it has never encountered an instance of its equipment causing security problems in countries where it operates.

Foreign Ministry spokesman Hong Lei on Thursday called for a "level and stable playing field" for Chinese companies operating overseas.

"As far as the report cited is concerned, it proves again that allegations against Huawei are unfounded," Hong said at a regular news conference.

"Chinese investments abroad are essentially mutually beneficial for relevant countries. We hope the countries can treat Chinese enterprises investing and running there in a proper way and create a level and stable environment."

Reuters contributed to this story.