US President Donald Trump and South Korean President Moon Jae-in on Sunday discuss North Korea's recent threats to cancel its unprecedented summit with Washington, Seoul's presidential office says.

South Korean President Moon Jae-in has credited US President Donald Trump for helping to spark the first inter-Korean talks in more than two years, and warned that Pyongyang would face stronger sanctions if provocations continued.

South Koreans go to the polls to choose a new president after Park Geun-Hye was ousted and indicted for corruption, and against a backdrop of high tensions with the nuclear-armed North.