The United States' top defense leaders expressed disappointment Wednesday over an ongoing dispute between South Korea and Japan that recently led to Seoul's decision to terminate an intelligence sharing pact with Tokyo.

At a joint press conference at the Pentagon, US Defense Secretary Mark Esper and Joint Chiefs of Staff Chairman Gen. Joe Dunford said they believe it is in the interest of all three countries to work together.

But in a departure from previous statements from the Pentagon or the State Department, the two appeared to direct their disappointment at both parties, not just South Korea.

"I was and I remain very disappointed that both parties are engaged in this," Esper said, adding that he is hopeful South Korea and Japan will be able to resolve their differences.

"We have common threats facing us -- North Korea and China, and bigger threats. And we're stronger when we all work together," he said.

Dunford said he has not seen any impact on military operations from Seoul's decision to pull out of the General Security of Military Information Agreement.

"But I share the secretary's disappointment in what I view as a setback in the relationship between South Korea and Japan. I think that's a very important relationship," he said.

South Korea announced its decision to pull out of GSOMIA last week, citing Japan's refusal to hold talks on resolving separate disputes on trade and shared history.

Washington has expressed concern and disappointment at the decision, saying the move creates challenges for trilateral security cooperation against North Korea's nuclear threats and China's military rise.

In Seoul, South Korean Vice Foreign Minister Cho Sei-young met with US Ambassador Harry Harris on Wednesday to ask that Washington stop airing its grievances.

Whether Esper and Dunford reflected that request in their comments is unclear.

But only hours earlier, Randall Schriver, US assistant secretary of defense for Indo-Pacific security affairs, reiterated Washington's concerns and called on South Korea to renew the pact.

GSOMIA is currently set to expire in late November.

Esper said the three countries share more interests and values than they do not, and need to collectively think about North Korea in the near term and China in the long term.

The focus should be on "how do we work together, how do we broaden our partnerships, strengthen our alliance and make sure we're prepared for the future," he said.

Asked if the US has contingency plans to deal with any fallout from the pact's termination, Dunford assured reporters there are other measures in place.

"We have other ways of sharing information, obviously none as effective as a very strong bilateral information sharing agreement between the two countries, but there are other mechanisms in place to allow us to deal with an alliance crisis or contingency," he said.

On North Korea's recent tests of short-range ballistic missiles, Esper said the US is concerned about them but will not "overreact" in the interest of renewing denuclearization talks.

"We're concerned about their short-range ballistic missile tests. We want to understand what they're doing, why they're doing, etc," he said. "But on the other hand, we're not going to overreact. We want to take a measured response and make sure that we don't close the door to diplomacy."

Expressing confidence that North Korea's "irreversible, verifiable, complete denuclearization" will be achieved, he stressed that the best way to meet that objective is through a political agreement.

North Korea has conducted seven rounds of missile tests since late July in apparent anger over Seoul-Washington military exercises that ended last week.

US President Donald Trump has dismissed them as unimportant, saying they do not violate an agreement by North Korean leader Kim Jong-un to refrain from long-range missile or nuclear tests.

Trump said earlier this month that in a letter to him, Kim stated his desire to resume denuclearization negotiations as soon as the exercises were over, but those talks have yet to take place.

Dunford also addressed reports that North Korea is building a new ballistic missile submarine and could be preparing for a test.

"I don't have anything to add to what has already been reported in the open press," he said. (Yonhap)