The State Department did say it welcomed China's efforts in the area after Beijing earlier called for the establishment of an effective international mechanism to prevent the spread of weapons of mass destruction.

"In a nutshell, we think that China has enacted good legislation on this issue and the focus is on implementation and enforcement," said State Department deputy spokesman Adam Ereli.

But he said there remain "ongoing" concerns on the issue.

"We don't sugarcoat them. It's an issue. And it's one that we're working cooperatively to address."

The United States frequently imposes sanctions on Chinese firms and state entities it accuses of evading proliferation controls and exporting missile components and other items useful in the production of weapons of mass destruction.

Though it voiced support for a global bid to stem the spread of weapons of mass destruction, China on Wednesday remained non-committal about joining the US-backed Proliferation Security Initiative (PSI).

"Unilateralism and double standards must be abandoned, and great importance should be attached and full play given to the role of the United Nations," said a State Council (cabinet) white paper on "China's Non-proliferation Policy and Measures."

The paper was published a day after Washington announced the addition of four new countries to the 11 nations already signed up to PSI which aims to implement widespread powers to seize suspected WMD in international waters and airspace.

John Bolton, the top US diplomat for arms control, said Canada, Denmark, Norway and Singapore would participate in the next meeting of countries involved in PSI.

Australia, Britain, France, Germany, Italy, Japan, the Netherlands, Poland, Portugal, Spain and the United States are already signed up to the project.

China has not announced its backing of the initiative, apparently due to concerns that the effort is largely aimed at containing its close ally North Korea.

Pyongyang is currently threatening to develop nuclear weapons to defend itself against the alleged threat of a US-backed Iraqi-style attack to remove Stalinist leader Kim Jong-Il.

WAR.WIRE