SEOUL, South Korea - North Korea's first successful launch of a three-stage, long-range rocket has outraged world leaders who consider it similar to a missile capable of attacking the United States, Europe, and other far-away targets. But experts say Pyongyang is years away from even having a shot at developing reliable missiles that could bombard the American mainland.

A missile program is built on decades of systematic, intricate testing, something extremely difficult for economically struggling Pyongyang, which faces guaranteed sanctions and world disapprobation each time it stages an expensive launch.

"One success indicates progress, but not victory, and there is a huge gap between being able to make a system work once and having a system that is reliable enough to be militarily useful," said Brian Weeden, a former U.S. Air Force Space Command officer and a technical adviser to the Secure World Foundation, a think tank on space policy.

North Korea's satellite launch Wednesday came after 14 years of painstaking labor, repeated failures, and hundreds of millions of dollars.

South Korea's Defense Ministry said Thursday that the satellite was orbiting normally at 4.7 miles per second, though it's not known what mission it is performing. North Korean space officials say the satellite would be used to study crops and weather patterns.

Though Pyongyang insists the project is peaceful, it also has conducted two nuclear tests and has defied international demands that it give up its nuclear weapons program.

The U.N. Security Council said in a brief statement after closed consultations Wednesday that the launch violates council resolutions against the North's use of ballistic missile technology, and said it would urgently consider "an appropriate response."

"This launch is about a weapons program, not peaceful use of space," U.S. State Department spokeswoman Victoria Nuland said. Even the North's important ally China expressed regret.

North Korea has long possessed the components needed to construct long-range rockets. Scientists in Pyongyang, however, had been trying and failing since 1998 to conduct a successful launch. Only this week did they do so.

In 2010, U.S. Secretary of Defense Robert M. Gates warned that within five years the North could develop an intercontinental ballistic missile capable of reaching the United States. Wednesday's launch suggests the North is on track for that, said former U.S. defense official James Schoff, now an expert on East Asia at the Carnegie Endowment for International Peace.

But he and other experts say the North must still surmount technical barriers to build the ultimate military threat: a sophisticated nuclear warhead small enough to mount on a long-range missile. And despite Wednesday's launch, Pyongyang is also lacking a credible long-range missile.

Other missing parts of the puzzle include an accurate long-range missile guidance system and a reentry vehicle able to survive the high speeds needed. Both are seen as years off.