Alexandra Bell, deputy assistant secretary of state for arms control, deterrence and stability, speaks during a forum hosted by The Korea Society in Washington, Nov. 22, in this photo captured from The Korea Society YouTube account. Yonhap

The United States believes that North Korea is prepared for a possible seventh nuclear test while awaiting "only a political decision" to go ahead, a senior U.S. official said Friday, warning another nuclear experiment would mark a "grave" escalation of regional tensions.

Alexandra Bell, deputy assistant secretary of state for arms control, deterrence and stability, made the remarks, reiterating America's "ironclad" security commitment to South Korea and its denuclearization objective for the Korean Peninsula.

"The United States assesses that the DPRK has prepared its Punggye-ri test site for its potential seventh explosive nuclear test, awaiting only a political decision to move ahead," Bell said during a forum hosted by The Korea Society. DPRK stands for the North's official name, the Democratic People's Republic of Korea.

"Such a test would constitute a grave escalation of tensions in the region and present a security risk to the entire world," she added.

Bell criticized Pyongyang's weapons tests this year, including that of a new Hwasong-19 intercontinental ballistic missile (ICBM), as a violation of multiple U.N. Security Council resolutions.

"Each missile launch (and) each nuclear saber-rattling speech is an indication that the DPRK is determined to advance its unlawful WMD and ballistic missile programs, underscoring the clear need to further grow and adapt our alliance with the ROK to better prepare to defend against potential attacks, including nuclear employment," she said, referring to South Korea's official name, the Republic of Korea.

"It goes without saying that the U.S. commitment to the defense of the Republic of Korea remains ironclad and our goal remains the complete denuclearization of the Korean Peninsula."

She also reiterated the allies' warning to Pyongyang that any nuclear weapons attack by the North against the South will be met with a "swift, overwhelming and decisive" response.

Bell underscored "remarkable progress" in the work of the Nuclear Consultative Group (NCG), the allies' key nuclear deterrence body launched last year as part of joint efforts to strengthen "extended deterrence," America's commitment to using the full range of its military capabilities, including nuclear arms, to defend its Asian ally.

A fourth NCG session will take place in Washington in early December, according to her. Bell represents the State Department at the NCG.

"In fact, the NCG's tremendous progress has been commended and endorsed by Presidents Yoon and Biden, including the completion of the U.S.-ROK guidelines for nuclear deterrence and nuclear operations on the Korean Peninsula," she said.

At the forum, South Korean Ambassador to the U.S. Cho Hyun-dong also mentioned the North's readiness to carry out another nuclear test, as he pointed out that the situation in East Asia remains a "tinderbox," with Pyongyang's "untethered" aggressiveness having the potential for "incitement at any time."

"In the case of North Korea, their antagonistic stance shows no sign of abating," he said.

"Beyond their traditional provocation and the recent release of multiple trash-filled balloons across the DMZ, they launched an ICBM merely days before the U.S. election — a strategic provocation that, though not unexpected, signals the likelihood that they are ready to conduct another nuclear test anytime."

Noting the presidential transition in the U.S., he expressed confidence for the future of the Seoul-Washington alliance.

"It is clear that even with the expected changes, our alliance will remain strong and continue to thrive," he said. (Yonhap)