Seoul said Sunday that Washington earlier in the day reaffirmed that it will shoulder the cost of deploying the THAAD anti-missile system in South Korea, after U.S. President Donald Trump said Seoul should pay for the $1 billion system designed to defend against nuclear-armed North Korea.

In a telephone call, Trump's national security adviser, H.R. McMaster, reassured his South Korean counterpart, Kim Kwan-jin, that the U.S. alliance with South Korea was its top priority in the Asia-Pacific region, the South's presidential office said.

The conversation followed another North Korean missile test-launch on Saturday that Washington and Seoul said was unsuccessful, but which drew widespread international condemnation.