The Trump administration made a clear break Thursday with diplomatic efforts to talk North Korea out of a nuclear confrontation, bringing the United States and its Asian allies closer to a military response than at any point in more than a decade.

Secretary of State Rex Tillerson said that 20 years of trying to persuade North Korea to abandon its nuclear program had failed and that he was visiting Asia "to exchange views on a new approach."

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.

North Korea has amassed a huge nuclear stockpile and appears at the brink of being able to strike the U.S. mainland and American allies in Asia. The rising threat from the isolated military dictatorship has prompted the Trump administration to begin assessing its options for how to respond and serves as an early test for how the president will confront an increasingly volatile international situation.

One potential immediate response would be to strengthen existing South Korean missile capabilities or to provide Japan with new offensive missile ability. Japan's defense chief told parliament this month that he would not rule out "first strike" capability, which would be a major departure from Japan's postwar pacifist traditions.

The United States could also field the same THAAD missile-defense system in Japan that it is now installing in South Korea or take the potentially provocative stop of reinstalling American nuclear weapons at U.S. bases in South Korea. The North Korean threat could also rekindle the largely dormant idea of a domestic U.S. missile defense system.

North Korea has boasted of an intercontinental ballistic missile, and experts on Asia security generally agree that such a capability is within Pyongyang's reach. Preventing it outright would probably require a military strike on North Korean facilities, something the United States has considered an option of last resort because it would almost certainly result in an attack on South Korea and U.S. forces stationed there, perhaps with chemical or biological weapons.

"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.

The country last month tested a missile that uses solid fuel, a big leap in its technological development, then this month fired a salvo of four missiles, part of what it said was a drill to practice hitting American military bases in Japan. Three of the four missiles landed in waters within Japan's exclusive economic zone.

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."

On Friday, Tillerson will be in South Korea, where more than 20 million people live within range of North Korean artillery. South Korea is conducting joint military exercises with U.S. forces, and installation of the THAAD system begins this month.

"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.