SEOUL, South Korea — Satellite images show that North Korea has halted work at a complex believed to have been intended to allow it to launch bigger and longer-range rockets, a Washington-based research organization reported on Tuesday.

The organization, the U.S.-Korea Institute at Johns Hopkins University, and others have been using commercial satellite imagery to monitor the complex, the Tonghae Satellite Launching Ground, in northeastern North Korea. They have previously detected the building of a new launching pad, missile assembly building and launch control center that they believe are designed to launch larger rockets capable of flying longer distances and delivering heavier payloads than the North’s Unha-3 rocket, which successfully thrust a satellite into orbit in December.

North Korea says it launches rockets for the peaceful purpose of sending scientific satellites into orbit. But Washington sees them as a cover for developing intercontinental ballistic missiles that could one day strike targets as far away as North America with nuclear warheads.

The institute first noticed that the work at Tonghae stopped at the end of 2012. In its latest update, posted on its Web site 38 North, it said on Tuesday that the construction had not resumed as of late May, although it was not clear what had caused the seven-month halt.