South Korea said it was seeking high-level talks this month with North Korea to prepare for a summit.

South Korea said on Friday it was seeking high-level talks this month with North Korea to prepare for a summit and that South Korean President Moon Jae-in may meet Donald Trump before the US president’s planned meeting with the North Korean leader.

Amid a flurry of diplomacy from Asia to Europe to Washington, Trump reaffirmed his plan to meet with North Korea’s Kim Jong Un by the end of May during a phone call on Friday with Moon and both voiced “cautious optimism” about efforts to resolve the crisis over North Korea’s nuclear weapons.

A White House statement said Trump and Moon discussed preparations for their upcoming engagements with Pyongyang and agreed that “concrete actions,” not words, were the key to denuclearization of the Korean peninsula.

They “emphasised that a brighter future is available for North Korea, if it chooses the correct path,” it said.

Washington has long included itself in the Korean dispute. It has heavy military presence in the region and uses North Korea’s ballistic and nuclear programs as a pretext to constantly threaten Pyongyang with military action.

That military posture has concerned the North, which says it needs to advance its weapons program to protect itself against potential US military action.