By intern researcher Julian Gewirtz

(Caijing.com.cn) Two prominent U.S. officials have publicly challenged the Chinese government's controversial plan to require Web filtering software in all PCs shipped after July 1.

A letter submitted by Secretary of Commerce Gary Locke and U.S. Trade Representative Ron Kirk to the Ministry of Industry and Information Technology (MIIT) and the Ministry of Commerce urged the Chinese government to revoke the mandate for Green Dam Youth Escort software.

Neither ministry had reacted publicly to the U.S. demand by the afternoon of June 25 in Beijing.

The letter followed a June 22 statement that the United States is "concerned" about the software requirement, which the Chinese government describes as a positive step to protect young people from pornography.

The U.S. Embassy in Beijing earlier told Caijing that the American government had conveyed its view to China.

The message parallels a rise in economic tension between the two countries. On June 23, the United States and European Union filed a complaint against China with the World Trade Organization, targeting Chinese restrictions on a host of raw materials.

In their letter, Locke and Kirk reiterated a U.S. request to "exchange views" with the Chinese government and industry officials.

"China is putting companies in an untenable position by requiring them, with virtually no public notice, to pre-install software that appears to have broad-based censorship implications and network security issues," Locke said in a press release announcing the letter.

Kirk's comments cited what he called China's "inappropriate means" of mandating "technically flawed" software. He also called the requirement a "serious barrier to trade," an argument advanced by a group of 19 international trade organizations that have petitioned MIIT.

The U.S. call is the latest bump in the road for a Chinese government plan that's been rocky from the start. Chinese lawyers, scholars and activists have raised a range of concerns, while the technical soundness of Green Dam has been a subject of intense debate as well.

In an email to Caijing, U.S. Embassy in Beijing spokesman Nicholas J.C. Snyder said Washington agrees with "concerns raised by Chinese citizens and international technology companies," and cited the "potential impact on trade and the free flow of information."

In addition to American government statements, Japanese officials have reportedly met MIIT officials to express concern over the software rule.