The US State Department was Monday perplexed by changes in the North Korean power structure, after Pyongyang's parliament promoted the powerful brother-in-law of leader Kim Jong-Il.

"Who knows?" said State Department spokesman Philip Crowley when asked to comment on why the changes were being made.

Jang Song-Thaek became vice-chairman of the National Defense Commission, the top decision-making body chaired by Kim, the official Korean Central News Agency (KCNA) reported, in a move seen as paving the way for Kim's youngest son to succeed him.

The parliament's rare second annual legislative session also sacked the prime minister in an apparent attempt to push harder to revive the ailing economy.

"We don't have any particular comment on the internal, you know, political machinations in North Korea," Crowley told reporters. "We certainly don't know, you know, why these changes are taking place at this time."

He renewed Washington's call for the denuclearization of the Korean peninsula and for Kim to stop his "provocative behavior."

"If some reformed North Korean leadership takes those steps, then they would be actually serving the interests of their people," Crowley said.

Meanwhile, a senior US official said a visit to Syria by North Korean deputy foreign minister Kim Hyong-Jun to discuss bolstering bilateral ties was a "dead-end."

"If Syria's looking to play a more constructive role in the world, it can start by dropping conversations like those," the official said.

earlier related report
S.Korea to send envoy to China over warship sinking
Seoul (AFP) June 7, 2010 - South Korea will send an envoy to China this week to seek support for its campaign for the UN Security Council to censure North Korea over the sinking of a warship, officials said Monday.

Vice Foreign Minister Chun Yung-Woo will visit China for two days from Tuesday, a foreign ministry spokesman told AFP.

Chun visited the United States last week as part of Seoul's diplomatic drive.

South Korea formally asked the council Friday to respond to North Korea's sinking of one of its warships in March with the loss of 46 lives, despite its communist neighbour's threat of retaliation.

UN ambassador Park In-kook told reporters he handed a letter to the council's chairman, Mexican ambassador Claude Heller, requesting action "commensurate with the gravity of the situation".

The South can expect support from the United States, Britain and France but China and Russia, the other two veto-wielding permanent council members, have not publicly stated their position.

A multinational investigation team said last month there was overwhelming evidence that a North Korean submarine fired a torpedo to break the Cheonan in two near the disputed border in March.

But China so far has not publicly condemned its ally the North and appealed only for restraint by all parties.

It says it will study the investigation findings but has not yet accepted an offer by the South to send a team of experts.

Russia sent naval experts who have ended their inspection, Seoul's defence ministry said Monday. The ministry said it was considering sending investigators to brief the UN on the findings of the probe.

South Korea has indicated it will not press for new UN sanctions on its neighbour.

US Defence Secretary Robert Gates said Saturday that Seoul might seek a Security Council statement denouncing Pyongyang instead of a full resolution.