The United States still hopes it can persuade China to abandon, or at least delay, its plan to require controversial filtering software on new computers, despite growing trade friction over the issue, a U.S. trade official said on Thursday.

The U.S. government will remain focused on the problem and use diplomatic and other available means as necessary to resolve it, said Debbie Mesloh, a spokeswoman for the U.S. Trade Representative's office one day after top American officials urged Beijing to drop the plan.

China's Ministry of Industry and Information Technology said on May 19 that all personal computers sold in China must have the Green Dam Internet filtering software as of July 1.

Chinese officials said the filter is necessary to prevent children from having access to pornographic websites.

But critics say the software, sold by Jinhui Computer System Engineering Co, is technically flawed and could be used to spy on Internet users and to block sites that Beijing considers politically undesirable.

U.S. Trade Representative Ron Kirk and Commerce Secretary Gary Locke urged China in a letter on Wednesday to abandon the plan, which they said would mean U.S. companies would be required to preinstall software that appears to have broad-based censorship implications and network security issues.

They objected to the short six-week notice that China gave for the new requirement and said there were complaints from global technology companies and media groups about the software.

If unresolved, the issue is likely to be a sore spot in upcoming U.S.-China meetings, including the Strategic and Economic Dialogue planned for late July, the Joint Commission on Commerce and Trade this autumn and meetings between President Barack Obama and Chinese President Hu Jintao around the Asia-Pacific Economic Cooperation summit in November.

Locke and Kirk also hinted at a possible case at the World Trade Organization, but those can take years to resolve.

One U.S. industry official, who asked not to be identified, said the Obama administration seemed to be emphasizing commercial concerns over the human rights aspect of the issue because China was more likely to respond to that.

The United States exported computers worth about $541 million and computer parts and accessories worth $1.5 billion to China last year. That paled in comparison to the $25 billion in computers and $27 billion in parts and accessories it imported from China in 2008.

(Reporting by Doug Palmer; editing by Chris Wilson)