Not close at all. MacArthur pushed to use nuclear weapons, but this was a strategic ploy. He wanted the Chinese (and, to a lesser extent, the USSR) to fear nuclear war. However, while MacArthur, as commander of the Far East, had nuclear bombs in Guam, they did NOT have their nuclear cores, which were in the mainland US, under the control of Atomic Energy Commission.

In April of 1951, 9 fully armed nuclear weapons WERE available in Guam, but MacArthur had been replaced by Matthew Ridgeway at that point. Ridgeway was given permission to use nuclear weapons at his discretion, but at that point, the war had already been fought to a stalemate and armistice talks would officially begin in July.

What would have happened if nuclear weapons had been used? Anyone's guess. Mao believed that the PRC could withstand a US nuclear attack, so as long as he remained in power, the PRC would not be dissuaded by nuclear attack. Stalin liked the Korean War because it forced the US to focus on Asia, hopefully to the detriment of Europe. No one knows what would have happened.