HONG KONG — One Chinese technology company receives crucial technical guidance from a former People’s Liberation Army rear admiral. Another company developed the electronics on China’s first atomic bomb. A third sells technology to China’s air-to-air missile research academy.

Their ties to the Chinese military run deep, and they all have something else in common: Each Chinese company counts one of America’s tech giants — IBM, Cisco Systems or Microsoft — as a partner.

Such links, which are generally not well publicized, are now at the center of a debate among some in the American defense community, including former United States military officials, analysts and others. While the cross-border partnerships, under which American tech companies share, license or jointly develop advanced technologies with Chinese counterparts, are a growth area for business, security experts are increasingly questioning whether the deals harm United States national security.

While the capabilities shared in the partnerships are commercial in nature, such technologies have also become more critical to defense. That is spurring concerns that widespread cooperation with Chinese companies could quickly increase China’s fundamental technological capabilities in a way that could easily help military research and operations.