TOKYO — U.S. Secretary of State Rex Tillerson hinted Thursday at a tougher strategy to confront North Korea's nuclear threat but said Pyongyang had no need to fear the United States, an alternately threatening and reassuring message that suggested the Trump administration is still formulating a clear policy.

In Japan at the start of a three-country Asia tour, Tillerson offered no details about what would comprise the "different approach" to North Korea the U.S. will pursue. He pointedly noted that 20 years of "diplomatic and other efforts" had failed to dissuade the isolated communist government from developing its nuclear program, which he called an "ever-escalating threat."

Speaking alongside Japanese Foreign Minister Fumio Kishida, Tillerson recited the longstanding U.S. demand that the North "abandon its nuclear and ballistic missile programs and refrain from any further provocation."

He said his visit to Asia was designed to "exchange views on a new approach," echoing the comments of others in Washington, who've said President Donald Trump wants to examine all options — including military ones — for halting the North's weapons programs before it becomes capable of developing a nuclear-tipped missile that could reach the U.S. mainland.

But if Tillerson's words were meant to put Pyongyang on notice, he quickly pivoted: "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."

State Department spokesman Mark Toner wouldn't specify Thursday what elements the new U.S. approach would entail. But he said Tillerson had sought to emphasize that the U.S. prefers a peaceful solution and that the U.S. was taking issue with North Korea's government, not its people.

Tillerson's trip, which will take him next to South Korea and China, comes as the Trump administration conducts a broad review of U.S. policy toward North Korea. Suggestions by Tillerson and others about a new direction have fueled speculation the U.S. may put greater focus on military options, which previous administrations have avoided.

Central to the U.S. review is China and its role in any bid to persuade Pyongyang to change course. China remains the North's most powerful ally.

While the U.S. and its allies in Seoul and Tokyo implore Beijing to press its economic leverage over North Korea, the Chinese have emphasized their desire to relaunch diplomatic talks — a non-starter for the U.S. under current conditions.

The U.S. and China also disagree over U.S. deployment of a missile defense system to South Korea. The U.S. says it's a system focused on North Korea. China sees it as a threat to its own security.

State Department officials have described Tillerson's effort this week as a "listening tour" as the administration seeks a coherent North Korea policy, well-coordinated with its Asian partners.

Thomas Karako, a senior fellow at the Washington-based Center for Strategic and International Studies, said that after so many years of failed diplomacy, it's inevitable the U.S. would consider more aggressive steps like military action.

"These are the things that have been have been on the back burner, but they're kind of what's left," Karako said. "North Korea doesn't have something to fear unless they act badly."

In Tokyo, Tillerson cited North Korea's missile launches this year as evidence of the worsening threat. In a sign of his host's emphasis on showing U.S.-Japanese resolve, Tillerson met with Japanese Prime Minister Shinzo Abe.

Last week, North Korea launched four missiles into seas off Japan, in an apparent reaction to major annual military drills the U.S. is currently conducting with South Korea. Pyongyang views the drills as a rehearsal for invasion.

In Beijing, a North Korean diplomat said Thursday that Pyongyang must act in self-defense against the drills, which he said have brought the region to the brink of nuclear war. He said the drills aimed at using atomic weapons for a pre-emptive strike against North Korea. Washington says the maneuvers are routine and defensive.

"The United States holds a joint military exercise every year to push the situation on the Korean Peninsula to a serious situation, and that is the source of the super tough measures we must take," Pak Myong Ho told reporters in a rare briefing at the North Korean Embassy in the Chinese capital. He spoke through a translator.

North Korea has accelerated its weapons development, violating multiple U.N. Security Council resolutions and appearing undeterred by tough international sanctions. The North conducted two nuclear test explosions and 24 ballistic missile tests last year. Experts say it could have a nuclear-tipped missile capable of reaching the U.S. within a few years.

During last year's election campaign, presidential candidate Donald Trump called into question U.S. security alliances and called for Tokyo and Seoul to contribute more for their defense. Tillerson, however, stressed that cooperation with Japan and South Korea was "critical."

Japan and South Korea both host tens of thousands of U.S. troops. Washington has been urging its two allies to step up security cooperation despite their historically strained relations.

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Lederman reported from Washington. Associated Press writer Gillian Wong in Beijing contributed to this report.