BEIJING, CHINA: China on Thursday stepped up accusations that Google is spreading obscene content over the Internet, a day after U.S. officials urged Beijing to abandon plans for controversial filtering software on new computers.

The growing friction over control of online content threatens to become another irritant in ties at a time the world is looking for the United States and China to cooperate in helping to pull the global economy out of its slump.

China's Foreign Ministry on Thursday accused Google's English language search engine of spreading obscene images that violated the nation's laws, less than 24 hours after disruptions to the company's search engines and other services within China.

Spokesman Qin Gang did not directly say whether official action was behind the disruptions, but he made plain the government's anger and said "punishment measures" taken against Google were lawful.

"Google's English language search engine has spread large amounts of vulgar content that is lascivious and pornographic, seriously violating China's relevant laws and regulations," he told a regular news conference.

A spokesman for Google in China declined to comment.

Separately, U.S. Commerce Secretary Gary Locke and U.S. Trade Representative Ron Kirk on Wednesday voiced concerns over the "Green Dam" software in a letter to Chinese 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 statement.

China says the "Green Dam" filtering software is to protect children from illegal images and insists the deadline of July 1 for new computers to be sold with the software will not change.

An official at the Chinese Ministry of Commerce, which handles trade rows, said the ministry had no immediate response to the U.S. criticism and referred questions to the Ministry of Industry and Information Technology, which also had no comment.

Critics have said the program, sold by Jinhui Computer System Engineering Co, is technically flawed and could be used to spy on users and block sites Beijing considers politically offensive.

The proposed new rules raised fundamental questions regarding the transparency of China's regulatory practices and concerns about compliance with WTO rules, the U.S. officials said.

Google disrupted

The software plan coincides with criticisms of Google by China's Internet watchdog and access disruptions in China to the U.S. company's websites.

The watchdog last week ordered the world's biggest search engine to block overseas websites with "pornographic and vulgar" content from being accessed through its Chinese-language version.

Late on Wednesday evening, Internet users in China were unable to open several Google sites for around an hour, and some reported disruptions throughout Thursday.

A company spokeswoman at Google in the United States said the firm was checking reports of problems with access in China.

The disruption -- coming soon after Google was criticised by China -- "seems beyond mere coincidence," said Mark Natkin, Managing Director of Marbridge Consulting, a Beijing-based company that advises on telecommunications and IT.

Google's problems reflect the difficulties of foreign Internet firms competing in the world's biggest online market while facing controversy over censorship.

Chinese officials have said their Internet moves are driven by worries about exposing children to disturbing online images, but an official newspaper reported on Thursday that a plan to recruit volunteers to scour the Internet for banned content and report to officials also has a political element.

The Legal Daily reported that 10,000 volunteers sought by Beijing would also search for "harmful content" that includes "threats to state security", "subverting state power", and "spreading rumours and disturbing social order".

Natkin, the consultant, said the official pressure was most unlikely to deter Google and other Internet companies from continuing to operate in China.

"Google has to be looking at China as a long-term play", he said. "The allure of the Chinese market, not just for Google and not just for Internet companies, is so compelling, so alluring."