Republican U.S. Senator John McCain on Wednesday raised concerns about the potential national security implications of a proposed bid by China's Tsinghua Unigroup Ltd's [TSHUAA.UL] to acquire U.S. chip maker Micron Technology Inc, and called for a thorough U.S. review. "I am concerned by the potential national security implications of a planned bid by a Chinese state-owned enterprise for Micron Technology, the last major American manufacturer of memory chips," the head of the Senate Armed Services Committee said in response to a query from Reuters.