Outgoing US Ambassador to South Korea Harry Harris said Tuesday that hope alone will not resolve the North Korea issue, highlighting the importance of combined exercises between Seoul and Washington amid the North's threat to continue developing its nuclear capabilities.

Harris made the remark at a webinar in Seoul, one day after President Moon Jae-in said South and North Korea can discuss issues regarding the allies' combined military exercises, if necessary, in response to the North's repeated calls to halt the joint maneuvers.

"While we hope for diplomacy with North Korea to be successful, we all can recognize that hope alone is not a course of action," the ambassador said, citing the North's "unrelenting pursuit of nuclear weapons" and China's "malign activities."

Seoul and Washington have held large-scale military exercises twice a year, and their springtime one is supposed to take place around March. North Korea has long bristled at such drills, claiming that they are a rehearsal for invasion into the North.

During a rare party congress earlier this month, North Korean leader Kim Jong-un demanded South Korea halt the combined exercise to improve the chilled cross-border ties between the two Koreas.

Harris said North Korea and China "will continuously test the resolve of our alliance and will seek ways to weaken our strong ties and sow doubt in order to divide us."

"There are ample historical examples of what could transpire including what happened on that fateful day almost 71 years ago, if we're not ready," he said, apparently referring to the outbreak of the 1950-53 Korean War.

Kim held three meetings with US President Donald Trump, but denuclearization talks have made little progress since their no-deal summit in Hanoi in February 2019.

On the transition of wartime operational control (OPCON) of South Korean troops from Washington to Seoul, the outgoing ambassador said it should not be rushed, acknowledging that the process is taking longer than some desire.

The current Moon Jae-in administration hopes to retake OPCON within his term that ends in May 2022, though the transition is not-time based but conditions-based.

"Our mutual security cannot be rushed. We want and need to take time to get this right," he said.

Regarding the South Korea-Japan ties, the US envoy stressed the importance of trilateral cooperation among the three countries amid growing concerns that the relations between Seoul and Tokyo could deteriorate following a recent court ruling on Japan's wartime sexual slavery issue.

"Notwithstanding the current tensions between Seoul and Tokyo, the reality is that no important security or economic issue in the region can be addressed without both," he said.

Moon said Monday that South Korea will seek dialogue with Japan to find a solution, referring to his two-track approach separating historical issues from efforts to forge "future-oriented" bilateral ties.

Tuesday's webinar, co-hosted by the Korea-US Alliance Foundation and the Korea Defense Veterans Association, took place one day before Harris' departure from the ambassadorial post which he assumed in July 2018.

"Going forward, you can rest assured that the Biden administration will continue the US efforts to further strengthen the US-ROK alliance," Harris said. ROK stands for South Korea's official name, the Republic of Korea.

Rob Rapson, the deputy chief of mission, will serve as charge d'affaires ad interim until a new envoy arrives. (Yonhap)