TOKYO — North Korea test fired a ballistic missile Sunday morning, its first launch in four months and the first since ­Donald Trump was elected president.

The South Korean Defense Ministry said the missile flew 310 miles, passed over the Korean peninsula, and landed in the Sea of Japan. It did not land in Japan’s waters, the ministry said.

South Korean officials said it appeared to be a medium-range ballistic missile rather than a long-range missile capable of reaching US territory. The launch came from the same region where Kim Jong Un’s regime fired a medium-range Musudan missile last October.

North Korea has threatened in recent weeks to test a long-range missile. There was no immediate comment from the North about Sunday’s launch.

The launch was made while Trump was hosting Prime Minister Shinzo Abe of Japan at his resort in Palm Beach, Fla.

In a brief joint appearance after the news of the missile test, the two presented a united front. Abe called the test ‘‘absolutely intolerable.’’ He said that in his summit with Trump at the White House on Friday the president ‘‘assured me the United States will always stand with Japan 100 percent.’’

After Abe spoke, Trump, who had been standing behind him, took the microphone and said: ‘‘I just want everybody to understand and fully know that the United States of America stands behind Japan, its great ally, 100 percent.’’

Some analysts thought the launch could have been the first stages of an intercontinental ballistic missile capable of reaching the United States.

‘‘I don’t think this is designed to respond to Trump; I think this is part of Kim’s continued efforts to try to advance his programs,’’ said Jon ­Wolfsthal, a senior nonproliferation official in the Obama administration who is now at Harvard’s Belfer Center. ‘‘But it has the added effect of calling Trump’s bluff.’’

“The real question is not what North Korea has done, but what the US is going to do about it,’’ Wolfsthal said.

The missile was fired shortly before 8 a.m. from a known test site in North Pyongan province in the west of the country, not far from the border with China, South Korea’s joint chiefs of staff said.

They were still working to analyze data from the projectile but said it appeared to be a Musudan missile, the type that North Korea had been trying to perfect last year. The Musudan has a technical range of about 1,800 miles.

Kim’s regime has declared a goal of creating an intercontinental ballistic missile capable of delivering a nuclear payload to the United States, and last year appeared to be making a concerted effort toward achieving that goal.

It held two nuclear tests and dozens of missile tests, including launching a series of Musudans in the summer.

But the regime has not fired any ballistic missiles since October, perhaps to avoid influencing domestic politics in the United States ahead of the presidential election and in South Korea, where the conservative president has been suspendedfrom office and there is now a good chance of a progressive administration that is friendlier to Pyongyang.

Or, analysts say, North Korea could have hit the pause button because it encountered technical difficulties.

In his New Year’s address, Kim said North Korea had conducted tests for a nuclear strike ‘‘to cope with the imperialists’ nuclear war threats’’ and said North Korea had ‘‘entered the final stage of preparation for the test launch of [an] intercontinental ballistic missile.’’

In response, President Trump tweeted: ‘‘North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the US. It won’t happen!’’

However, apart from repeating the usual pledges to work stop North Korea from reaching its nuclear goals, the Trump administration has said little on what it would do to stop Kim.

The administration is understood to be forming an official view of North Korea after eight years in which the Obama administration practiced ‘‘strategic patience’’ — hoping that it could wait out North Korea.

Though Pyongyang has been relatively quiet about the transfer of power to Trump, its state media has repeatedly called for Washington to abandon its ‘‘hostile policy.’’