During the early stages of the Korean War, General of the Army Douglas MacArthur was a proponent of liberating the entire Korean Peninsula from communist influence. President Truman and Secretary of State Dean Acheson felt that if this plan was followed it would cause the Communist Chinese to enter the war and expand it beyond acceptable limits.
Following the Inchon landing, General MacArthur's United Nations troops pushed the North Koreans north to the Yalu River, the border between North Korea and China. General MacArthur advocated attacking Chinese forces, but was denied this action by President Truman and Secretary Acheson. General MacArthur then began to publicly disagree with his Commander in Chief and to seek to weaken him politically with the support of U.S. Senators, including Joe McCarthy.
President Truman's statement on April 10, 1951 can be found at the link below.