South Korea Says It Will Launch Spy Satellites as Missile Deal Is Revised

SEOUL, South Korea — The South Korean government said on Tuesday that it would begin work on launching its own military surveillance satellites to monitor North Korea, after negotiating a loosening in an agreement with the United States that limits the kind of rockets it is permitted to develop.

South Korea and the United States have just finished negotiations to revise their so-called missile guidelines, first signed in 1979, under which Washington maintained tight restrictions on what type of missiles and rockets Seoul could develop, Kim Hyun-jong, a senior national security aide to President Moon Jae-in, said in a news briefing on Tuesday.

Mr. Kim denied that the easing of the missile guidelines had been part of negotiations over how much South Korea should pay annually to help cover the cost of keeping 28,500 American troops in the South. President Trump has insisted on a sharp increase from this year’s 1.04 trillion won ($866 million), accusing South Korea of not spending enough for its own defense.

Under the revised guidelines, Mr. Kim said, Washington has removed the limit on how powerful solid-fuel rockets South Korea can build to launch space vehicles. Solid-fuel rockets are much easier to store and handle than their liquid-fuel counterparts, making them ideal for missile engines.

The lifting of the cap allows South Korea to build powerful rockets with potential applications for long-range ballistic missiles. Seoul remained obliged not to build ballistic missiles with a range of more than 800 kilometers, or 497 miles, Mr. Kim said, but hoped to start launching low-orbit military surveillance satellites using its own solid-fuel rockets within the next several years.

“I cannot go into classified military details but I can tell you that we will soon have many low-orbit military satellites with excellent surveillance capabilities monitoring the Korean Peninsula from the sky 24 hours a day,” Mr. Kim said.

South Korea has no military satellites of its own, relying instead on United States spy satellites to monitor North Korea. But with Mr. Trump questioning the merit of keeping United States troops in South Korea even as the North’s nuclear and missile capabilities have rapidly expanded, Seoul has struggled to augment its own abilities to counter the North Korean threat.

South Korea plans to deploy five military reconnaissance satellites by 2023 at a cost of $1 billion, the national news agency Yonhap reported.

On Tuesday, Mr. Kim said that South Korea has lacked “eyes and ears” despite its $41.6 billion defense budget, partly blaming restrictions in the missile guidelines.

Under those guidelines, the United States provided South Korea with technical help in building missiles. But it also imposed restrictions on missile developments because of concern over a regional arms race. The guidelines have been revised three times before.

In 2012, as the North’s missile threat increased, the United States agreed to let South Korea possess solid-fuel ballistic missiles with a range of up to 497 miles as long as the payload did not exceed 500 kilograms, or about half a ton.

In 2017, the United States lifted the payload limit. But South Korea is still banned from developing ballistic missiles with a range of more than 497 miles.

South Korea test-launched a new short-range ballistic missile, Hyunmoo-4, in March. The missile had a 497-mile range but was designed to carry a payload of up to two tons, according to South Korean news media.