WASHINGTON, Feb 26 (Reuters) - Pilots at American Airlines (AMR) requested on Tuesday the United States not strike any air deal with Hong Kong to permit an alliance between the world's biggest carrier and Cathay Pacific Airways Ltd. (0293) until Cathay improves its labor practices. In a letter to Transportation Secretary Norman Mineta, the Allied Pilots Association said Hong Kong's flagship carrier and Asia's fourth-largest airline has openly defied contractual obligations with its pilots. The airline and its pilots union, the Hong Kong Air Officers Association, are locked in a bitter dispute over pay and benefits as well as working conditions and scheduling. A work-to-rule campaign by the pilots, who claim the company has intimidated them, has led to flight delays and cancellations. Cathay Pacific countercharges that the union is insincere, has hurt business, and has unfairly characterized the carrier as an unsafe airline. Transportation Department negotiators are in Hong Kong this week for air talks that could produce a limited accord that would allow Cathay and American to launch a new code-share agreement. This prospect concerns the American pilots who say the Cathay pilots are under siege. "We respectfully request that you conclude no agreements expanding access to U.S. destinations for Cathay Pacific until the employment and human rights of the Cathay Pacific pilots are safeguarded," wrote John Darrah, president of the Allied Pilots Association.