Soon after Tillerson’s remarks, in a sign of mounting tensions, the North Korean Embassy held an extraordinary news conference in Beijing to blame the potential for nuclear war on the United States while vowing that its homegrown nuclear testing program will continue in self-defense.

“I think it’s important to recognize that the political and diplomatic efforts of the past 20 years to bring North Korea to the point of denuclearization have failed,” Tillerson said.

The secretary of state’s reference to decades of failure alluded to the carrot-and-stick diplomacy that began with a 1994 deal between the United States and North Korea. Under it, Pyongyang would have received aid and two proliferation-resistant nuclear power plants in return for freezing and eventually dismantling its nuclear weapons program.

That deal collapsed in 2002, and North Korea achieved its first atomic test in 2006. The George W. Bush administration’s efforts at a new deal collapsed, and Pyongyang has managed to build up its stockpile of nuclear material as well as refine its missiles despite what on paper look like crushing international sanctions.

North Korea’s nuclear and missile efforts have intensified under dictator Kim Jong Un, who took power in 2011, and appear to have escalated further since Donald Trump’s election.

Tillerson’s remarks reflected growing agitation in Washington that a tougher stance on North Korea is required.

Sen. Bob Corker (R-Tenn.) said during a Senate Foreign Relations Committee hearing last month that the United States has three choices: what he called “proactive regime change,” to topple Kim; sanctions and other coercive measures; or military cooperation with Japan and South Korea that could include a preemptive strike on missile facilities. “Otherwise, we’re staring down the barrel of an ICBM,” Corker said.

Tillerson made a version of Trump’s argument that the United States will demand clear benefits for its diplomacy and foreign aid and will walk away when necessary. Tillerson scoffed at the U.S. expense for trying to entice North Korea to drop its nuclear program — $1.35 billion by his count.

“That encouragement has been met with further development of nuclear capabilities, more missile launches,” including this month and last, Tillerson said. “In the face of this ever-escalating threat, it is clear that a different approach is required.”

“The joint military exercises by the hostile forces are aimed at preemptive strikes against the DPRK,” North Korean Embassy official Pak Myong-ho said, referring to the official name of his country, the Democratic People’s Republic of Korea. “Therefore, the peace and stability of the Korean Peninsula is under serious threat,” he said. “Now the situation is already on the brink of nuclear war.”

Pak said the exercises could “turn into real combat at any time.”

While strident North Korean warnings about the annual military exercises are common, calling a news conference in a third country to drive the message home was a dramatic step. China is North Korea’s protector and only ally, and Beijing is the only capital where the North could so quickly summon Western reporters.

Tillerson’s last stop on his six-day trip will be in China, which remains skeptical of any U.S. military response.

Last week, Chinese Foreign Minister Wang Yi warned that the United States and North Korea were like “two accelerating trains” on a collision course, while Premier Li Keqiang cautioned Wednesday that “tension may lead to conflict.”

There are sharply different views in the region about how to lower the North Korean threat, with China in particular unwilling to do anything that might destabilize the desperately poor agrarian nation on its border.

Under discussion in addition to potential military moves are tighter U.S. sanctions on the regime and secondary sanctions against its commercial allies. Those steps are considered largely symbolic unless China uses its economic leverage to slow or end North Korean import of critical missile parts.

The Trump administration has signaled that it could increase financial penalties against Chinese companies and banks that do business with North Korea.

Tillerson’s remarks seemed to shut the door on any rekindling of international talks that had involved Japan, South Korea and China to persuade the dynastic regime to stop firing missiles and pursuing nuclear weapons.

The failed diplomatic outreach had coincided with U.S. efforts to reassure North Korea that it did not plan an unprovoked attack — something the North has long claimed is a Washington plot.

In his opening remarks in Tokyo, Tillerson appeared to give a nod to those reassurances, however. “North Korea and its people need not fear the United States or their neighbors in the region who seek only to live in peace with North Korea,” he said.

Tillerson is the former chairman and chief executive of ExxonMobil and has no previous diplomatic experience. He has kept a low profile since assuming his new job and has not attended some meetings with foreign leaders in the Oval Office, leading to speculation that he has little influence within the Trump administration.

Tillerson did not go to the U.S. Embassy in Tokyo to meet staff Thursday morning, as is often customary. He instead stayed in his hotel, where he read and received briefings from embassy officials, a spokesman said.