WASHINGTON -- The United States is closely monitoring the possibility of North Korea conducting its seventh nuclear test, which if conducted, will prompt a robust response from the US, National Security Advisor Jake Sullivan said Wednesday.

He, however, said the US remains open to dialogue and will continue to do so.

"We are also watching very closely the continuing possibility of a nuclear test, to which we would also have a robust response," Sullivan told reporters aboard Air Force One while en route to California with President Joe Biden for the upcoming Summit of Americas there.

His remarks come one day after US Special Representative for North Korea Sung Kim said the US and its allies will have a "swift response" against any North Korean nuclear test.

Sullivan earlier said the North may conduct a nuclear test any time during or after Biden's trip to South Korea and Japan that concluded late last month. Officials in Seoul believe Pyongyang may conduct a nuclear test as early as this week. North Korea conducted its sixth and last nuclear test in September 2017.

"We cannot do anything other than take the course of action that we think is strong, steadfast and clear, and that is an openness and willingness to engage in diplomacy if North Korea is prepared to come to the table, and an absolute and resolute commitment to defending our allies in the ROK in Japan," Sullivan said when asked if a North Korean nuclear test would mean failure for US policy toward the recalcitrant country that would in turn require a change in US policy.

ROK stands for the Republic of Korea, South Korea's official name.

"That's the position we have taken. We think it's the right position, and it's a position we will sustain as we go forward," added Sullivan.

North Korea staged 18 rounds of missile tests this year, already marking the largest number of missile tests in a single year, according to the state department.

Sullivan insisted the tests have only strengthened US alliances.

"We continue to obviously monitor and respond to the tests that they have been conducting," he said.

"One thing that it has done is only further cemented the strength of our alliances with both the ROK and Japan, and we have been able to conduct joint exercises with both of them in response to some of these launches," he added. (Yonhap)

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