National Security Advisor Jake Sullivan speaks about President Biden's up-coming trip to Asia, as well as Sweden and Finland's desire to join NATO, at the White House in Washington, May 18. EPA-Yonhap

North Korea is widely expected to stage a long-range missile or nuclear test before or even during President Joe Biden's trip to South Korea and Japan, U.S. National Security Advisor Jake Sullivan said Wednesday.

He said the U.S. is fully prepared to make any necessary adjustments to its defense posture to ensure the security of the U.S. and its allies.

"With respect to the issue of North Korea, we have said from this podium, we said at the State Department and we have indicated in quite clear terms that our intelligence does reflect the genuine possibility that there will be either a further missile test, including long range missile test, or a nuclear test or frankly both in the days leading into, on, or after the president's trip to the region," Sullivan said in a press briefing at the White House.

"We are preparing for all contingencies, including the possibility that such a provocation would occur while we are in Korea or in Japan," he added.

Biden is set to embark on a trip to South Korea and Japan this week, beginning with a three-day visit to Seoul from Friday (KST), followed by a three-day visit to Tokyo.

North Korea has staged 16 missile launches this year, and the State Department has said the recalcitrant country may be preparing to conduct a nuclear test as early as this month.

Pyongyang recently began reporting COVID-19 cases for the first time since the pandemic began over two years ago, prompting many to believe that the country may refrain from staging additional provocations, including a nuclear test, to prevent the spread of COVID.

However, State Department Press Secretary Ned Price said there was no "expectation" of any delays when asked Tuesday.

Sullivan reiterated that the U.S. is prepared for all possibilities.

"We are prepared, obviously, to make both short and longer-term adjustments to our military posture as necessary to ensure that we are providing both defense and deterrence to our allies in the region, and then we're responding to any North Korean provocation," he said.

The top security advisor noted that Biden's trip will highlight his commitment to U.S. alliances with the two countries, as well as to the entire region.