SEOUL, South Korea — A recent string of unsuccessful missile tests by North Korea, and the release of a video showing the launch of a different weapon, reflected a frantic drive by its leader, Kim Jong-un, to bolster his political standing before a high-profile dialogue with China, analysts said on Thursday.

North Korea conducted the latest of those tests on Tuesday, only hours before its envoy — Ri Su-yong, a confidant of Mr. Kim and a Politburo member — arrived in Beijing. The weapon, an intermediate-range Musudan ballistic missile, exploded as soon as it was fired, South Korean military officials said.

The Musudan, which analysts say was devised to strike United States military bases in Guam with nuclear and chemical weapons, had not had a test flight until April, when North Korea launched three. Each test failed.

Despite having little time to fix the problems, engineers conducted another test on Tuesday, also unsuccessful, an unusual streak of flops even by the checkered standards of North Korea.