WASHINGTON -- The United States has discussed with China the growing concerns over a possible North Korean nuclear test, US National Security Advisor Jake Sullivan said Thursday.

He also reiterated US concerns over what will be North Korea's seventh nuclear test.

"On North Korea, we have expressed our concern that North Korea is preparing to conduct another nuclear test. We have said that publicly. We have communicated that to China," Sullivan said in an online discussion session hosted by the Center for a New American Security (CNAS), a Washington-based think tank.

The remarks come after Sullivan met with Yang Jiechi, head of the Chinese Community Party's foreign affairs bureau, in Europe.

"The proof will be in the pudding. Let's see how things play out, but both of these subjects featured in our discussions on Monday in Europe, the discussion I had with my counterpart, Yang," he said when asked if there existed any consensus between the US and China on the war in Ukraine and North Korean provocations.

Kurt Campbell, deputy assistant to the president and National Security Council coordinator for the Indo-Pacific, later said the US and China had "detailed" and "frank" discussions.

"We had a detailed and very frank set of discussions about Ukraine, about North Korea, about Southeast Asia, about the Indo-Pacific strategy, keeping those lines of communication open, trying to remove areas of potential miscalculation, trying to make sure that there are communication links in the case of inadvertence or miscalculation," he said of the Sullivan-Yang meeting in a later session hosted by CNAS.

"That is the primary pursuit as we try to build what is undeniably a competitive relationship, but hopefully a peaceful relationship in which the best aspects of competition on both sides can be brought out," he added.

China, together with Russia, blocked a US-proposed UN Security Council resolution last month that sought to impose fresh and tougher Security Council sanctions on North Korea for staging more than a dozen rounds of ballistic missile tests this year in violation of existing Security Council resolutions.

Pyongyang has so far fired more than 31 ballistic missiles in 18 rounds of missile tests this year, according to US officials.

Officials in Seoul and Washington have noted the North may also conduct its seventh nuclear test in the near future, with South Korean Foreign Minister Park Jin reaffirming earlier this week that Pyongyang appears to have finished all preparations for a test and the only thing left before an actual test may be a political decision.

North Korea conducted its sixth nuclear test in September 2017. (Yonhap)