SEOUL/WASHINGTON, May 4 (Reuters) - South Korea's national security adviser is in Washington to meet his U.S. counterpart, John Bolton, ahead of an expected summit between U.S. President Donald Trump and North Korean leader Kim Jong Un, officials in Washington and Seoul said.

The U.S. National Security Council asked Chung Eui-yong to fly to the United States to discuss matters related to the summit, a South Korean presidential official told reporters on Friday.

The United States had asked that the visit be kept quiet due to the issues to be addressed at meetings there, said the official, who declined to be identified.

A senior administration official in Washington confirmed Chung's visit and his meeting with Bolton.

South Korea has been working closely with old ally the United States on efforts to rein in North Korea's development of weapons.

South Korean President Moon Jae-in and North Korea's Kim pledged to work for the "complete denuclearisation" of the Korean peninsula at a summit on their heavily fortified border on April 27.

North Korea says it is ready to discuss denuclearisation and give up its nuclear programme as long as the security of Kim's regime is guaranteed.

Among issues to be decided before Trump can meet Kim are where and when they will hold their summit.

Trump has suggested holding the meeting, which is expected in late May or early June, at the border village of Panmunjom in the demilitarised zone between the two Koreas.

This would require close coordination with Seoul, although officials in the South Korean president's office have said there has been no official requests to prepare the venue for the summit.

Chung may address the issue of a venue in Washington but he was more likely to discuss a "bigger deal" with U.S. officials pertaining to North Korea, the South Korean official said.

Chung was last in Washington shortly before the Moon-Kim summit. (Reporting by Christine Kim in SEOUL and Steve Holland in WASHINGTON Editing by Robert Birsel)