Efforts by Chinese smartphone maker Huawei to enter the U.S. market have just encountered a major roadblock. American telecom AT&T has abandoned a deal with Huawei to sell its flagship smartphone, the Mate 10 Pro, due to national security concerns in Congress.

Chinese tech giant Huawei faces another major setback in expanding its U.S. smartphone market. A letter from the U.S. Senate and House intelligence committees to the Federal Communications Commission shows that lawmakers are concern about Chinese companies in the U.S. telecom sector. The lawmakers were especially concerned with the Huawei-AT&T partnership to launch consumer products in the U.S. The letter also noted that, the committees were concerned about Chinese espionage in general, and Huawei's role in the process. Huawei said in a statement that the U.S. market presents unique challenges and it remains committed to the effort. Huawei said that privacy and security are always its first priorities. Huawei is the world's third largest smartphone marker by volume after Apple and Samsung. However it has only half a percent share of the U.S. smartphone market, compared with 39 percent for Apple and 18 percent for Samsung.