A top South Korean presidential aide handling national security affairs will have to adjust his plan to visit Washington in September, especially as the Barack Obama administration is preoccupied with the Syrian crisis, an informed source said Sunday.

Kim Jang-soo, head of the national security office at Cheong Wa Dae, initially planned to travel to the U.S. this month, which would have been his first trip here since taking the post in February.

"Kim has been pushing for a trip to Washington for meetings with National Security Advisor Susan Rice and other senior U.S. officials," the source said. "In particular, Kim wants to have discussions on the timing of OPCON transfer."

The source was referring to an agreement that South Korea will regain wartime operational control of its troops from the U.S. as of 2015.

The OPCON transition was originally slated for 2012 but was postponed until 2015 at the request of Seoul following North Korea's deadly torpedo attack on a South Korean warship in 2010.

The Park Geun-hye administration is seeking another delay to the transfer, citing the North's growing nuclear and missile threats. The U.S. remains cautious about further pushing back the OPCON transfer.

Kim, a former defense minister and lawmaker, reportedly hopes to lay the groundwork for resolving the issue before the allies hold their annual defense ministerial talks in early October.

While serving as Seoul's defense minister in 2007, Kim visited Washington to ink a deal with then-Pentagon chief Robert Gates on a 2012 OPCON transfer schedule.

The source said, however, it appears to be difficult to arrange Kim's meetings with Rice and other officials within September, as the American government is busy dealing with the Syria issue and preparing for the U.N. General Assembly in New York, which is to take place starting on Sept. 23.

"South Korea and the U.S. are unlikely to produce a new agreement on the OPCON transfer schedule during the upcoming defense ministerial talks. They would need more time to discuss it," the source said. (Yonhap News)