Washington,  North Korea is believed to be "continuing preparations" for a nuclear test while the US is set to face any threat posed by the "recalcitrant" country, a state department spokesperson has said.

Department Press Secretary Ned Price said on Monday that the US also remains open to engaging in dialogue with Pyongyang, Yonhap news agency reported.

"Our concern regarding the potential for another North Korean nuclear test, which would be its seventh, has been consistent for some time now. We assess that the DPRK is preparing its Punggye-ri test site for what would be its seventh test," Price said in a daily press briefing, referring to North Korea by its official name, the Democratic People's Republic of Korea.

"We are preparing for all contingencies in close coordination with our partners and allies around the world," he added.

The spokesperson noted steps to be taken by the US may include "adjustments" to US defence posture.

"We are prepared to make both short- and longer-term adjustments to our military posture as appropriate in responding to DPRK provocation and as necessary to strengthen both defense and deterrence to protect our allies in the region," he said.

The remarks came as Deputy Secretary of State Wendy Sherman began a three-day visit to Japan earlier in the day for bilateral and trilateral talks with her South Korean and Japanese counterparts.

Price said much of Sherman's ongoing trip to Tokyo will be "dedicated to discussing the challenge that the DPRK poses to the region."

The department spokesperson also reiterated US commitment to engage in dialogue with the North.

"We have made consistently clear that we harbor no hostile intent towards the DPRK. We remain open to dialogue. We remain open to diplomacy," he said.

"At the same time, our commitment to the security of our personnel in the region, of our treaty allies is ironclad," added Price.

John Kirby, spokesperson for the White House National Security Council (NSC), expressed concerns over North Korea's recent provocations, while highlighting the possibility of a potential nuclear test.

"We have been consistently concerned about North Korean provocations. It's not just because they have accelerated missile launches, for instance, in the last few weeks. It's been a consistent concern of ours, which is why several months ago, again, we added some intelligence capabilities off the Korean Peninsula to help us get a little bit better insight," he said in a telephonic press briefing.

North Korea fired nearly a dozen ballistic missiles in just three weeks from late September, bringing the total number of ballistic missiles it launched this year to 44, the largest number of ballistic missiles fired in a single year, according to US officials.

"We have said that the North Koreans could conduct the nuclear test at any time. We still believe that's the case," said Kirby.

The NSC strategic communications coordinator also reaffirmed US commitment to engage in dialogue with Pyongyang, saying the US has offered to sit down with the North "without preconditions."

"And that offer stands today. No preconditions. We are willing to sit down and start to have a dialogue."