The United States will "decisively" respond to any threats from North Korea that may occur during President Joe Biden's trip to Asia, a White House official said Thursday amid speculation that Pyongyang could carry out a missile or nuclear test while the U.S. leader is visiting South Korea and Japan.

"Our cooperation with these two countries bilaterally and the U.S.-Japan-ROK cooperation trilaterally will only strengthen in the face of any further provocations by North Korea," National Security Adviser Jake Sullivan told reporters aboard Air Force One, using the acronym for the Republic of Korea, South Korea's official name.

U.S. National Security Adviser Jake Sullivan. (Getty/Kyodo)

Sullivan said Wednesday that U.S. intelligence has suggested a "genuine possibility" of North Korea staging another missile test, including a potential long-range missile test, or a nuclear test, or both, around Biden's nearly weeklong trip to the region from Thursday.

Asked how such provocation by North Korea may affect Biden's first trip to Asia as president, Sullivan said it will "only serve to reinforce and highlight the fact that the United States is going to be engaged in the Indo-Pacific, is going to be a stalwart ally, and is going to stand up to and not shrink from any acts of aggression."

The United States is prepared for any such "eventualities" and is coordinating closely with its two closest Asian allies, he emphasized.

In March, North Korea conducted its first launch of an intercontinental ballistic missile since November 2017, marking an end to a self-imposed moratorium on test-firing such missiles that had stretched back to April 2018.

Pyongyang has not tested nuclear devices since September 2017, but speculation is growing that the secretive country is also moving closer to scrapping its moratorium on nuclear tests.

Sullivan said Washington has also been conveying to China, a key ally of North Korea, that further provocations from Pyongyang would only cause the United States to increase its "fortitude" in terms of defending its allies, and may prompt adjustments to the way the American military has been postured in the region.

The Biden administration has reiterated that it is open to talks with North Korea and will remain prepared to meet anywhere without any preconditions to make progress toward the goal of the denuclearization of the Korean Peninsula.

But Sullivan said Pyongyang has "not displayed any indication of willingness to engage in meaningful or constructive diplomacy."

"As long as they continue to refuse to do so, we'll continue to stay on the course we're on, which is to impose pressure, to coordinate closely with our allies, and to respond to provocations with clarity and decisiveness," he said.