But Mr Trump said maximum sanctions and pressure on North Korea would continue ahead of proposed talks in May.
He added that denuclearisation of the Korean peninsula was now a possibility.
The comments follow Mr Kim's meeting with China's President Xi Jinping, in his first known foreign trip since taking office in 2011.
Mr Kim and his wife were greeted with a banquet and a guard of honour, with the North Korean leader reportedly saying he was committed to denuclearisation. China is North Korea's main economic ally.