China’s industry and information technology ministry has cast the order as a move to shield children from obscene or violent Internet sites. But critics and technology specialists here and abroad have called it an ill-concealed effort to rein in online criticism of the government and other speech that Beijing considers subversive.

China’s Internet community has mounted a blistering attack on the requirement since it became public in early June, and even some state-controlled publications have questioned its wisdom. American and European governments and businesses have almost unanimously protested the order, saying it would curb free speech and compromise the security of foreign companies’ computer operations inside China.

The state-run Xinhua news agency, which reported the postponement, offered no background on the decision, and did not say how long the delay might last. But many computer makers have declined to say how they would comply with the requirement, apparently hoping that the government would delay or reverse its decision under international pressure.

In Beijing, a US Embassy spokesperson said the government welcomed the announcement. American officials have worried publicly that the initiative could stifle free speech, and Washington had officially warned China that the requirement could violate free-trade agreements.

China’s Ministry of Industry and Information Technology, which licensed the technology from two Chinese developers, says that the software automatically blocks Web surfers from seeing “unhealthy Internet content’’ like pornography and violence.