Washington,  The US will respond quickly to a future nuclear test by North Korea if necessary, a Pentagon spokesperson has said.

Sabrina Singh, deputy spokesperson for the defence department, made the remark as she highlighted the possibility of a North Korean nuclear test in the near future, Yonhap news agency reported.

"We are in very close touch with our allies and partners in the region, and should there be such a test, we would be able to respond quickly if needed," Singh said when asked about the possibility of a North Korean nuclear test.

Seoul and Washington earlier said the North may have completed all preparations for what will be its seventh nuclear test.

"So we remain concerned about the prospects of any nuclear test. We know that the North Koreans have made preparations for such a test," the Pentagon spokesperson said in a daily press briefing.

"And this assessment, you know, remains consistent with what we have said from the beginning, but we certainly would remain concerned and which is why and you heard the secretary and his ROK counterparts speak to this yesterday," she added, referring to South Korea by its official name, the Republic of Korea.

Defence Secretary Lloyd Austin noted in his meeting with South Korean Defense Minister Lee Jong-sup on Thursday that any nuclear attack by Pyongyang against the US or its allies will result in the "end" of the North Korean regime.

Austin also agreed to employ US strategic assets in and around the Korean Peninsula to a level "equivalent to the constant deployment" of such assets to help deter or counter North Korean provocations.

Singh declined to comment when asked how the US planned to boost the presence of its strategic assets in the region, but highlighted the importance of joint military drills.

"I don't have anything to announce today on any new deployment of strategic assets, but I think Vigilant Storm, the exercise that's ongoing now, speaks for itself," she said, referring to the joint military exercise of South Korea and the US.

"These exercises increase confidence in our joint operations, and again this is not the last exercise. We will continue to do exercises with South Korea or Japan when opportunities present itself," she added.

John Kirby, spokesman for the White House National Security Council, also underscored the importance of defense readiness and capabilities amid heightened tension on the Korean Peninsula following a series of North Korean provocations.

"Obviously, we remain deeply concerned about the provocations that the Pyongyang regime continues to demonstrate here and it seems like almost on a daily basis. It's all leading to just more insecurity and instability on the peninsula and in the region," he said in a virtual press briefing.

Pyongyang has fired more than 50 ballistic missiles this year, including more than a dozen since late September.

Kirby reiterated that the US remains committed to engaging with North Korea, but said the Kim Jong-un regime continues to remain unresponsive.

"We'd love to be able to solve this issue diplomatically, but short of that and since we have no signs that the Kim regime is interested in that, we've got to make sure we've got the appropriate military capabilities ready to go if needed," he said.