The United States government believes that several Chinese companies are violating United Nations sanctions and providing Iran with assistance in improving its missile technology and developing nuclear weapons, the Washington Post quoted a senior U.S. official as having said Sunday.

According to the report, the U.S. has asked Beijing to do more to end these companies' contact with Iran. An anonymous U.S. official told the paper that the U.S. State Department submitted a "significant list" of such companies and banks to Chinese officials last month.

"My government will investigate the issues raised by the U.S. side," Wang Baodong, a spokesman for the Chinese Embassy, told the Washington Post.

The Post reported that the U.S. official did not name any Chinese companies but said U.S. intelligence believes several are giving restricted technology to Iran, mostly for its missile program.

Iran denies Western allegations that it is seeking nuclear weapons, insisting that its uranium enrichment program is for peaceful energy purposes only.

The most recent UN resolution aimed at curtailing Iran's nuclear ambitions calls for measures against new Iranian banks abroad if a connection to the nuclear or missile programs is suspected, as well as vigilance over transactions with any Iranian bank, including the central bank.

The first two Iran sanctions resolutions adopted in 2006 and 2007 passed unanimously. The council approved a third set of sanctions in 2008 with 14 yes votes and one abstention.