China says a U.S. decision to impose sanctions on four Chinese companies for allegedly helping Iran acquire missile-related technology would seriously undermine Beijing and Washington's cooperation in non-proliferation.

China lashed out at the United States for freezing the U.S. assets of four Chinese companies and not allowing them to conduct transactions with Americans. 

Chinese Foreign Ministry spokeswoman Jiang Yu says Washington imposed the sanctions without showing evidence of wrongdoing. 

"The U.S. wrong practice severely undermines our non- proliferation cooperation and will not benefit the development of bilateral relations," she said.  "We require the U.S. side to change their practice and abandon completely the wrong practice of sanction and pressure."

Washington imposed sanctions on the Chinese companies and one American company Tuesday for supplying Iran with missile-related parts and items that could contribute to weapons of mass destruction. 

This is not the first time the United States has sanctioned the four Chinese companies.  The U.S. government imposed sanctions against them in 2004 for transferring to Iran restricted equipment and technology. 

President Bush signed an executive order last year authorizing strong financial sanctions against those who provide services or support to governments that spread the development of weapons of mass destruction.

Washington has designated Iran a "state sponsor of terrorism" and has sought to put pressure on Tehran for refusing to cooperate with the International Atomic Energy Agency (IAEA) on its nuclear programs. 

China has resisted pressuring Iran, but has agreed, along with the United States and Russia, to a package put forward by Britain, France, and Germany to persuade Iran to abandon its nuclear ambitions.

This week, Iran's president is in China for meetings of the Shanghai Cooperation Organization (SCO), which has indicated it will invite Iran to formally join the group of Central Asian nations, Russia, and China.

U.S. officials have criticized the SCO invitation to Iran.  Last week Defense Secretary Donald Rumsfeld said it was strange for an organization that is supposed to fight terrorism to invite, what he called, one of the leading "terrorist nations" to its meeting.