South Korean army soldiers ride on a military truck towing the artillery in Paju, South Korea, Friday, Sept. 9, 2016. (Im Byung-Shik/AP)

The world’s leaders expressed outrage and alarm Friday over North Korea’s latest nuclear test, as Pyongyang’s accelerating nuclear program is emerging as a major national security threat that a new U.S. president will confront.

In a White House statement, President Obama condemned Friday’s test as “provocative and destabilizing” and a “grave threat” to regional and international stability. He said the United States and its allies will seek new U.N. sanctions and take other measures “to demonstrate to North Korea that there are consequences to its unlawful and dangerous actions.”

“To be clear, the United States does not, and never will, accept North Korea as a nuclear state,” he said.

The United Nations, which in March imposed some of the harshest economic sanctions ever against North Korea, called an emergency meeting to discuss the test, which state news media claimed now allows Pyongyang to produce nuclear warheads small enough to attach to ballistic missiles. The latest test, North Korea said, was its biggest yet, although it may take several days to determine how powerful it was.

At the United Nations, diplomats called for more resolutions and actions.

Jean-Marc Ayrault, the foreign minister of France, a permanent member of the Security Council, said North Korea’s latest “provocation cannot be left without consequences, especially at the U.N. Security Council.”

Secretary General Ban Ki-moon condemned what he called a “brazen breach” of U.N. resolutions.

“I count on the Security Council to remain united and take appropriate action,” he told reporters. “We must urgently break this accelerating spiral of escalation.”

Secretary of State John F. Kerry said the United States would work with other Security Council members to take “robust steps” in response, and he urged North Korea to resume denuclearization talks it abandoned in 2009.

“We remain open to credible and authentic talks aimed at full and verifiable denuclearization of the DPRK,” he said, referring to the country’s official name, the Democratic People’s Republic of Korea. “Sadly, the DPRK has chosen a different path and made clear it would not be a credible negotiating partner.”

Other leaders used particularly blunt language to denounce what Australian Prime Minister Malcolm Turnbull called North Korea’s “reckless, provocative, dangerous” actions.

South Korea accused the North’s leader, Kim Jong Un, of “fanatic recklessness.” South Korean President Park Geun-hye said his mental state is “spiraling out of control.”

Japan branded North Korea an “outlaw nation in the neighborhood.” Russia insisted that Pyongyang “stop its dangerous escapades.” The International Atomic Energy Agency said North Korea had displayed “complete disregard of the repeated demands of the international community.”

Even China, Pyongyang’s only ally and its economic lifeline to the outside world, said it was “resolutely opposed” to the test and warned North Korea to refrain from further actions that would worsen the situation.

Although North Korea is not believed to be capable of delivering warheads to the U.S. mainland, it is considered a threat on U.S. troops in South Korea and Japan.

North Korea’s fifth missile test, its second this year, reflects the stepped-up pace of its nuclear missile program. After a test in January, the Security Council imposed sweeping new sanctions that bar most trading with the regime for anything other than food, medicine and other humanitarian purposes. But the sanctions have done nothing to stop the government’s determination to further its quest to develop ballistics missiles with nuclear warheads. Nor is it clear that further sanctions would be a deterrent.

“The current sanctions-only approach, however tough, is simply not working, and continuing on that track is a recipe for even greater failure,” said Daryl Kimball, executive director of the Arms Control Association. “The next president, even before Inauguration Day, will have to have a strategy in place to try to effectively engage with the North to try to leverage the sanctions regime in place to achieve some restraint on North Korea’s nuclear missile activities.”

The latest test comes as several countries and institutions are on the cusp of transition. Ban, a diplomat from South Korea, will finish his term by the end of the year. South Korea will hold presidential elections next year. And U.S. elections are two months away.

Despite a number of failed missile tests this year, North Korea’s nuclear ambitions have barely been mentioned in this year’s U.S. presidential race. Experts on North Korea and nuclear nonproliferation said the latest nuclear test could change that.

“The U.N. has passed five Security Council resolutions and had a major General Assembly vote condemning North Korea for human rights ­abuses,” said Victor Cha, a Korea scholar at the Center for Strategic and International Studies. “But the problem is none of this is working. And whether it’s Clinton or Trump, this is going to be the number one issue. There is no bigger security threat to the homeland than this.”

Though it is difficult to assess North Korea’s claims about the potency of its nuclear test, experts say it underscores the regime’s determination to mass-produce warheads and eventually to deploy them on missiles in the field.

“If it doesn’t have the capability to threaten its neighbors with nuclear weapons yet, it will at some point, probably sooner rather than later,” said James Acton, a physicist who is co-director of the Nuclear Policy Program at the Carnegie Endowment for International Peace. “People disagree about whether there’s any chance of threatening the continental United States at the moment. But the trajectory is clear.”

So far, nobody has come up with a policy or reaction likely to convince Pyongyang to stop or slow down its nuclear program. Scott Snyder, director of the Program on U.S.-Korea Policy at the Council on Foreign Relations, said the threat is growing as the strategy of patience is proving futile and the potential for confrontation grows.

“The current administration’s policy has been pursued because of the perception that there was still time to turn North Korea around,” he said. “But the closer Kim Jong Un gets to having a direct-strike capability, the greater the pressure will be, presenting a new administration with only two options — acquiescence to North Korea as a nuclear state, and use of military force in order to deprive North Korea of that capability. That’s basically the territory we are entering.”