In this Nov. 6, 2019, file photo, U.S. Ambassador to Seoul Harry Harris poses for photos during a meeting at the Foreign Ministry in Seoul. AP

Outgoing U.S. 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.

This Friday, Aug. 16, 2019, photo provided Saturday, Aug. 17, by the North Korean government, shows test firings of an unspecified new weapon at an undisclosed location in North Korea. Korean Central News Agency via AP-Yonhap

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.