MOSCOW - Russia has information on North Korean plans to launch a ballistic missile but does not know when it will take place, Interfax news agency quoted a senior Russian military source as saying on Wednesday.

We have certain information about the type and characteristics of the missile. However, we do not have accurate data on the timing of its launch, said the source, who was not identified.

North Korea has angered many in the international community with missile launches, threats to attack South Korea and a May 25 nuclear test.

U.S. and South Korean forces have raised a military alert on the peninsula to one of its highest levels since the 1950-53 Korean War.

At the United Nations on Tuesday, world powers edged toward an agreement on a resolution expanding sanctions on North Korea because of its nuclear test and weapons program, but were unable to close the deal, diplomats said.

South Korean Defense Minister Lee Sang-hee said in an address to troops that North Korea's military grandstanding was linked to leader Kim Jong-il's succession plans in the inhumane state, an aide said on Wednesday.

South Korean legislators said they had been briefed by the South's spy agency and told that the North's leaders had started the groundwork that would allow Kim's youngest son, Swiss-educated Jong-un, to take over power.

Analysts say the show of military strength might help Kim to divert attention from an faltering economy that has grown worse under his rule and boost support after a suspected stroke about a year ago that raised questions over his iron grip on power.

His economy could take another hit as the United States and Japan have pushed for strong sanctions to punish North Korea for its nuclear test, but China and Russia have been cautious about provoking Pyongyang by imposing more embargoes.

(Reporting by Conor Sweeney; Editing by Ralph Gowling)