Foreign Ministry Spokesman Sun Yuxi says China has worked hard to implement an agreement reached last November with the United States not to help other countries develop ballistic missiles capable of delivering nuclear weapons. Under that agreement, China also pledged to improve its system of controlling missile-related exports.

Mr. Sun told a news conference after Secretary of State Powell's talks with Chinese officials that China has stuck to its promise. Mr. Sun said China feels that the United States has failed to honor some of its commitments on certain issues. But he declined to provide further details.

Under the agreement, the United States waived sanctions against China for past missile transfers to Iran and Pakistan, and said it would agree to resume processing licenses for U.S. satellite launches in China. But Mr. Powell told reporters Saturday that there were still problems to be resolved before the United States could approve some satellite sales to China.

Still, Mr. Sun confirmed that experts from both countries will hold new talks to try to resolve their differing views over arms proliferation. And he agreed with Mr. Powell that bilateral relations are improving on the whole. But Mr. Sun again criticized U.S. sales of sophisticated weapons to Taiwan, saying that the weapons help Taiwan independence forces and interfere with China's internal affairs.

The spokesman also said that China is open to further talks regarding U.S. missile defense, indicating a softening of China's previously hard-line opposition to the system.