The United States said its embassies will not stop tweeting reports on air quality readings in Beijing and Shanghai, which have annoyed mainland authorities.
"This is an initiative by the embassy in Beijing, by the mission in China, to convey useful information to our citizens abroad," State Department spokesman Mark Toner said.
"It's primarily directed to American citizens. But we don't have any problem if the Chinese want to access this information." Toner said the US embassy has no plans to stop sending out the reports on its dedicated Twitter feed called - BeijingAir - which has 20,000 followers.
"The monitoring and publishing of China's air quality are public interest and reserved for the government," Wu Xiaoqing, vice minister of environment protection, said.
Wu did not name the US, but called on embassies to abide by the law.