WASHINGTON -- The press secretary for the US Department of State reiterated the importance of trilateral cooperation between the US, South Korea and Japan on Monday, saying the countries will be more successful when working together.

The remarks from Ned Price came after Japanese Vice Foreign Minister Takeo Mori boycotted a joint press event with his South Korean and US counterparts -- Choi Jong-kun and Wendy Sherman -- following their three-way talks in Washington last week.

"When it comes to the relationship between our allies, Japan and the Republic of Korea, you are right that Deputy Secretary Sherman had an opportunity to meet trilateral with her counterparts here in Washington last week," the department press secretary said in a daily press briefing, referring to South Korea by its official name.

Price added the US has consistently underscored the importance of the trilateral relationship, "knowing that when it comes to all of our common interests ... when it comes to North Korea, when it comes to issues like climate change, economic prosperity and growth, everything we are trying to achieve will be more successful if we have a deep trilateral relationship."

The press conference following the vice ministerial talks here last week was originally set to be held jointly by Sherman and her South Korean and Japanese counterparts, but was held unilaterally by the US diplomat alone as Mori refused to take part.

Mori was later said to have taken issue with a recent trip by the head of South Korea's national police to Dokdo, a set of South Korean islets in the East Sea, to which Tokyo often lays territorial claims.

Choi has said he had flatly dismissed Japan's protest, along with its renewed claim to Dokdo, and that he had agreed to his US counterpart holding a press conference by herself on the outcome of their trilateral meeting because of its importance.

"I can tell you and I think you heard this directly from the Deputy Secretary that the trilateral session itself was very constructive. It was a good meeting," Price said.

"It was an opportunity for the three countries to compare notes, to discuss many areas, shared areas of concern, to discuss our common objective." (Yonhap)