Nuclear-armed North Korea fired two short-range missiles into the Sea of Japan early Thursday morning, the Japanese and South Korean defense ministries said, in an apparent bid by Pyongyang to heap pressure on the U.S. amid stalled denuclearization talks.

“North Korea fired one short-range missile at around 5:34 a.m. and the other at 5:57 a.m., from the Hodo Peninsula near its eastern coastal town of Wonsan,” the South Korean Joint Chiefs of Staff said in a statement.

The missiles fell into the sea before reaching Japan’s exclusive economic zone and posed no security threat, Kyodo News reported, quoting a Japanese government source.

The South Korean military said one missile flew around 430 km while the other appeared to have traveled 690 km and that it “seems to be a new type of missile.”

Experts said the 690-km range meant that U.S. Marine Corps Air Station Iwakuni in Yamaguchi Prefecture, home to a squadron of the U.S. military’s advanced F-35B stealth fighter jets, was within striking distance.

Ankit Panda, a senior fellow with the Federation of American Scientists, wrote on Twitter: “690 km gets this missile mighty close to being able to strike the USMC Air Station at Iwakuni. A more southerly launch point would cover Iwakuni.”

There has been precedent for such strategic planning by the North.

In March 2016, it test-fired what experts said were likely four extended-range (ER) Scud missiles, with the official Korean Central News Agency issuing an overt claim that the drill was a rehearsal for striking U.S. military bases in Japan.

Both of Thursday’s missiles flew at an altitude of around 50 km, pointing to the possibility that the weapons could be similar to ones launched in May by the North.

Experts said those missiles — likely a Scud-C or KN-23 — bore a strong resemblance to the Russian-designed Iskander, a short-range, nuclear-capable ballistic missile that has been in Moscow’s arsenal for more than a decade.

In Tokyo, Defense Minister Takeshi Iwaya said that Japan was still analyzing whether the projectiles were, in fact, ballistic missiles.

If they were the same type of missiles fired in May, Iwaya said Thursday’s launches would constitute a violation of U.N. sanctions resolutions banning North Korea from using such technology.

The U.S. delivered a relatively muted initial response to the launch, suggesting that U.S. President Donald Trump hopes to refrain from being overly critical amid Washington’s stalled nuclear negotiations with Pyongyang.

“We are aware of reports of a short-range projectile launched from North Korea,” a senior administration official who spoke on condition of anonymity told The Japan Times. “We have no further comment.”

The White House said long-stalled working-level talks with the North over its nukes were due to restart sometime this month after Trump and North Korean leader Kim Jong Un met on June 30 at the Demilitarized Zone dividing the two Koreas, injecting fresh momentum into the negotiations.

But Pyongyang has expressed frustration with Washington and Seoul in recent weeks, warning on July 16 that if the United States did not halt a joint military drill with South Korea scheduled for next month, it might scuttle efforts to kick-start the negotiations — and even potentially resume nuclear and longer-range missile tests.

The U.S. and South Korea have said that the 19-2 Dong Maeng (alliance) exercise will go ahead in August, though Seoul has hinted that they could undergo a name change. On Tuesday, Kim inspected a “newly built submarine” that was to operate in the Sea of Japan, state-run media reported, in one of the first displays of power related to his country’s nuclear capabilities since November 2017.

Photos with the report showed Kim and accompanying officials standing near the vessel, dwarfed by what was likely a ballistic-missile submarine built to be capable of launching nuclear-tipped missiles.

North Korea’s last public display of its nuclear weapons program came in November 2017, when it tested a Hwasong-15 intercontinental ballistic missile (ICBM). The Trump administration acknowledges that the missile is capable of striking deep within the United States.

Since then, it has kept to a self-imposed moratorium on nuclear and long-range missile tests amid the denuclearization talks.

Trump admitted Monday that a new round of the talks had not been scheduled, but added that “when they’re ready, we’ll be ready.”

Adding to the uncertainty, North Korean Foreign Minister Ri Yong Ho is also reportedly unlikely to attend the ASEAN Regional Forum to be held in Thailand early next month, though it has sent its foreign minister to the forum every year since 2003. U.S. Secretary of State Mike Pompeo is scheduled to attend the forum, and it was thought the two top diplomats would have a chance to hold talks on the sidelines. Jean Lee, a former Associated Press bureau chief in Pyongyang who now heads the Washington-based Wilson Center think tank’s Korea Program, said that while the White House played down Thursday’s launch, the tests are based on a long-held goal.

“It’s alarmingly strategic: With Trump willing to overlook #NorthKorea’s short-range launches, Kim has focused on building weapons capable of terrorizing #SouthKorea & #Japan,” Lee wrote on Twitter. “He wants to divide the allies by raising the fear of conflict, pressuring neighbors to push for action.”

“If ever there’s a time when #SouthKorea & #Japan should put aside differences to look at the larger picture — of regional security — it’s now,” she added. “But I fear these actions, by U.S. & #NorthKorea, will only spur debate on whether they should build their own nuclear weapons.”