American experts say U.S. arms sales to Taiwan remain an obstacle in non-proliferation talks with China.

The closed-door meeting was meant to give all sides a chance to express their views on non-proliferation in an informal setting.

On the agenda of this Fifth U.S.-China Conference on Arms Control, disarmament and non-proliferation were some key topics. They include how to better enforce export controls, possible changes to the Non-Proliferation Treaty, and the process of getting North Korea to dismantle its nuclear weapons programs.

Symposium participants said U.S. and Chinese experts agreed Beijing and Washington should work together to bring about changes in the Non-Proliferation Treaty to include provisions on non-state actors, the individuals who traffic in nuclear technology that could end up in the hands of terrorists.

One of the meeting's organizers is Professor William Potter, who heads the Center for Non-proliferation Studies at the Monterey Institute of International Studies in California. Speaking after the conclusion of the symposium, he said Chinese officials raised the issue of Taiwan as one that could hamper negotiations.

"There clearly are major differences about Taiwan and how that may be linked to broader cooperation in the non-proliferation sphere, and I think after this meeting, both sides better appreciated the others' views, but I cannot say that we closed the gap that much on the Taiwan issue," he said.

China opposes U.S. weapons sales to Taiwan, which it considers a renegade province. Beijing has said the issue is a central theme in its relations with Washington.

The United States says it does not support independence for the Taiwan, but stands by the Taiwan Relations Act - a U.S. law that requires Washington to defend the self-governed island if China were to attack.

Acting Assistant Secretary of State Susan Burk said that despite the contentious Taiwan issue, she found the talks with Chinese officials and experts productive.

"They made very clear what their views are on that issue and we heard their views," said Susan Burk. "I think in the larger strategic context, it was expected."

In remarks at the opening ceremony on Tuesday, Chinese Vice Foreign Minister Zhang Yesui said Beijing wants to participate in efforts with the United States and other countries to improve global non-proliferation and prevent weapons of mass destruction from landing in the hands of terrorists.

He said China has fully enacted laws restricting the export of nuclear, biological, chemical and missile technologies as part of its effort to combat proliferation.