Mr. Moon, since winning the election last month, has vowed to pursue talks with North Korea, insisting that sanctions alone have failed to persuade the North to stop its nuclear weapons program. He is scheduled to meet with President Trump in Washington this month to discuss a joint strategy on how to stop the North’s pursuit of nuclear weapons.

“I am a believer in dialogue, but I also know that dialogue is possible when we have a strong national defense,” Mr. Moon was quoted as saying from the missile test site. “A policy of embracing North Korea is possible when we have a defense capability that surpasses that of North Korea.”

The North has been stepping up its missile development in recent years. A series of tests that it has conducted have raised fears that it is bolstering its abilities to strike South Korea, Japan and American military bases in the Western Pacific. The North has also pledged to develop an intercontinental ballistic missile that could deliver a nuclear warhead to the continental United States.

As that threat by the North has increased, South Korea has also sought to strengthen its abilities, particularly after the United States agreed in 2012 to let it possess ballistic missiles with a range of up to 497 miles, as long as the payload did not exceed 500 kilograms, about half a ton. South Korea can load warheads weighing up to two tons on ballistic missiles with shorter ranges.

Until then, the South had been barred from deploying ballistic missiles with a range of more than 300 kilometers, or 186 miles, and a payload of more than half a ton because of concerns about a regional arms race. It first agreed to missile guidelines with the United States in 1979 in return for American technological aid in developing its first ballistic missiles.