U.S. officials say Defense Secretary Robert Gates has called off plans to travel to China this week because the Chinese government said the timing of a planned visit was "not convenient."
Gates had hoped to visit China to discuss cooperation between the U.S. and Chinese militaries. U.S. officials did not give a reason for China's reluctance to host the defense secretary.
The Chinese government has delayed several high-level military exchanges in recent months in apparent protest at Washington's decision in January to allow a major arms sale to Taiwan to go ahead.
China views Taiwan as a renegade province that must be reunited with the mainland, by force if necessary. U.S. officials say Taiwan needs updated weapons to improve its defense capabilities.
Gates was due to leave Washington Wednesday on an international tour that takes him first to Singapore for a regional security conference.
Gates had planned to travel to China after his Singapore visit. U.S. officials say he hopes to reschedule the trip at a later date.
China is sending officials to the Singapore conference, but U.S. Defense Department spokesman Geoff Morrell says Gates does not intend to meet them because Washington believes they are not senior enough.
Morrell says Washington and Beijing should have a continuous high-level engagement and must not allow such a dialogue to be disrupted by "bumps in the road," as he put it.
U.S. officials have said they want to resume military contacts with China to avoid misunderstandings that could lead to confrontations.
Some information for this report was provided by AP, AFP and Reuters.