U.S. President Donald Trump invited North Korea’s Kim Jong-un to shake hands during a possible visit to the demilitarized zone with South Korea.

Trump is scheduled to visit South Korea later Saturday after meetings at the G20 summit in Osaka, Japan.

He tweeted Saturday morning that “after some very important meetings, including my meeting with President Xi of China,I will be leaving Japan for South Korea (with President Moon). While there, if Chairman Kim of North Korea sees this, I would meet him at the Border/DMZ just to shake his hand and say Hello(?)!”

Trump’s summit with Kim in Vietnam earlier this year collapsed without an agreement for denuclearizing the Korean Peninsula.

The White House on Friday declined to comment on whether Trump was scheduled to go the DMZ.

U.S. special envoy Stephen Biegun said on Friday the U.S. was ready to hold constructive talks with North Korea to follow through on a denuclearization agreement reached by the two countries last year, South Korea’s foreign ministry said.

Biegun told his South Korean counterpart, Lee Do-hoon, that Washington wanted to make “simultaneous, parallel” progress on the agreement reached at a summit between Trump and Kim in Singapore last year, the ministry said in a statement.

Both sides agreed to establish new relations and work towards denuclearization of the Korean Peninsula.

But negotiations have stalled since a second summit in Vietnam in February collapsed as the two sides failed to narrow differences between U.S. calls for denuclearization and North Korean demands for sanctions relief.