People pass by a TV showing a file image of North Korea's missile launch on Wednesday during a news program at the Seoul Railway Station in Seoul, South Korea. North Korea on Wednesday fired projectiles toward its eastern sea, South Korea's military said, in an apparent display of its expanding military capabilities ahead of planned nuclear negotiations with the United States this weekend. The sign reads: "North Korea launched an unspecified missile." Credit: Ahn Young-joon | AP

TOKYO — North Korea launched a ballistic missile test into the sea off Japan on Wednesday, a short while after announcing a resumption of negotiations with the United States over its nuclear program, in what appeared to be a calculated show of strength.

South Korea said the ballistic missile had been launched from the sea, possibly from a submarine, a development that underlines North Korea’s continued progress in missile development and its ever-growing military threat.

The State Department called on North Korea to “refrain from provocations, and abide by its obligations under U.N. Security Council Resolutions.”

It also encouraged Pyongyang to “remain engaged in substantive and sustained negotiations to do their part to ensure peace and stability on the Korean Peninsula and achieve denuclearization.”

The launch came the day after North Korea announced negotiations between the two sides will formally begin on Saturday, marking the first official talks since President Trump met Kim Jong Un in June.

South Korea’s presidential Blue House said it “placed weight on the possibility” the missile was launched from a submarine off North Korea’s east coast. But a U.S. official, who was not named, told CNN the missile was launched from an underwater platform, although it was designed to function as a submarine-launched ballistic missile.

Japan’s government spokesman Yoshihide Suga initially said the country had detected two ballistic missiles, but later said it may have been one missile that broke into two pieces, adding that one piece may have landed in the waters of Japan’s Exclusive Economic Zone.

On Tuesday, North Korean Vice Foreign Minister Choe Son Hui said the two countries “agreed to hold a working-level discussion on October 5th, following a preliminary contact on the 4th,” according to a statement carried by the state-run Korean Central News Agency.

“I expect the working-level talks to accelerate positive developments in DPRK-U.S. relations,” Choe said, using the initials of her country’s official name, the Democratic People’s Republic of Korea. “Our representatives are ready to attend the working-level talks with the United States.”

State Department spokeswoman Morgan Ortagus also told reporters that officials from the two countries plan to meet “within the next week.”

South Korea’s Joint Chiefs of Staff said North Korea fired the ballistic missile from the sea northeast of the city of Wonsan, saying it had flown a distance of 280 miles, to an altitude of about 570 miles.

David Wright, co-director of the global security program at the Union of Concerned Scientists, noted that the missile had been fired with a lofted trajectory.

“If flown on a standard trajectory with the same payload, that missile would have a maximum range of about 1,900 km (1,200 miles),” he wrote in a blogpost. “This would classify the missile as medium range (1,000 to 3,500 km).”

Japanese Prime Minister Shinzo Abe told reporters the launch violated U.N. Security Council resolutions, adding “we strongly condemn and protest the act.”

The missile test was a reminder of North Korea’s military capabilities, and an indication that it intends to drive a hard bargain in the talks, experts said. It can also be seen as an implicit threat — that if it doesn’t get what it wants in the negotiations, it could ratchet tensions up higher.

South Korea said it presumed the missile was a Pukkuksong type. Ankit Panda, a nuclear expert at the Federation of American Scientists, said it was likely to be the Pukkuksong-3, a new submarine-launched ballistic missile that has been under development for a while. In July, Kim Jong Un was also seen inspecting a new submarine thought to be capable of firing ballistic missiles.

“It shows Kim Jong Un is making progress on developing the sea leg of his nuclear forces,” Panda said. “It’s clear the sea leg isn’t just a vanity project or a prestige project, but they see it as something worth spending resources on, to improve their deterrence in a crisis.”

Lee Ho-ryung a researcher at the Korea Institute for Defense Analyses in Seoul, said North Korea had been developing its submarine capacity for a while, so the test was not a surprise.

“Submarine-launched ballistic missile poses a bigger threat than other short-range missiles North Korea displayed over the past year,” she said. “By displaying this a day after announcing plans for working-level talks, North Korea is implying that its weapons capacity will continue to be improved while negotiations are stalled.”

Panda said the timing of the launch was probably an attempt to increase North Korea’s bargaining power in the talks with the United States, as well as a protest against South Korea’s display this week of new F-35 stealth fighters obtained from the United States, and Japan’s plans to deploy the Aegis Ashore missile defense system.

Negotiations between the two countries’ diplomats have been frozen since the breakdown of a summit between Trump and Kim in Hanoi in February. Another meeting between the two leaders at the demilitarized zone between the two Koreas in June was supposed to lead to a resumption of negotiations, but the stalemate persisted until now.

Meanwhile, North Korea has conducted short-range ballistic missile tests, while complaining bitterly about joint military exercises carried out by the United States and South Korea. On Monday, North Korea blamed the stalling of the dialogue on Washington and Seoul, accusing them of failing to keep their promises.

North Korea has also insisted that talks will succeed only if the United States takes a different approach than its tack in Hanoi, but it has been careful not to criticize Trump directly.

Indeed, the North Korean Foreign Ministry also said last week that Trump is “different from his predecessors in political sense and decision” and that it hoped he would make a wise, bold decision.

Washington Post writers Min Joo Kim and Akiko Kashiwagi contributed to this report.