SEOUL, South Korea — A second test of what appeared to be an advanced missile engine, part of what North Korea said on Saturday was part of a “reliable strategic nuclear deterrent,” left little doubt that the country is moving quickly toward resuming the program that led to a crisis with Washington two years ago.

While the North gave no details, it said it had conducted “another crucial test” on Friday night at a missile-engine and satellite-launching site that leader Kim Jong-un had once promised President Trump he was about to close. It was the second such test in a week, and came after weeks of increasingly vocal attempts to press the United States into further talks and new concessions.

All the available evidence indicated it was some kind of advanced missile engine, and the wording of the North Korean announcement strongly suggested it was part of a renewal of the country’s nuclear delivery systems.

American analysts and intelligence experts said they believe the ground test — conducted at a stationary stand designed to demonstrate experimental missile-engine designs — was intended as a signal that the country could soon resume testing of an intercontinental ballistic missile.