A top security adviser for South Korean President Yoon Suk Yeol said on Wednesday he had offered to step down.

His resignation comes ahead of Yoon’s summit with U.S. President Joe Biden next month.

Media reports said earlier National Security Adviser Kim Sung-han could be replaced over planning issues related to Yoon’s visit to Washington.

Kim said he had wanted to return to academia after laying the groundwork to restore the country’s alliance with the U.S. and improve its relations with Japan, according to a message released by Yoon’s office.

He added that Yoon’s upcoming trip to the United States was being well prepared so his successor could take over smoothly.

Yoon nominated Cho Tae-yong, ambassador to the United States, as Kim’s successor, Yonhap news agency reported following the announcement.