Kim Jong-il, at right, succeeded his father, Kim Il-sung, at left, in 1980 [AFP/HO/KCNA via KNS]

North Korea has has announced a reshuffle of three senior officials just days before a crucial ruling communist party meeting that is expected to outline a change in the country's leadership.

State media on Thursday reported the promotion of three diplomats ahead of the Workers' Party of Korea meeting described as "historic".

All three of the newly promoted diplomats have been involved in international negotiations on the disarmament of North Korea's nuclear programme.

The announcement came as North Korea prepared for its biggest political meeting in decades. The meeting next week is expected to pave the way for a power transfer from Kim Jong-il, the North Korean leader, to his son, Kim Jong-un.

The Korea Central News Agency (KCNA) said Kang Sok-ju, the North Korean first vice-minister of foreign affairs, was made a vice-premier of the cabinet.

Kang, known to be overseeing Pyongyang's nuclear negotiations and diplomatic policies on the US, accompanied the North Korean leader during his visit to China last month.

Kim Kye-gwan, the country's chief negotiator in the six-nation nuclear disarmament talks, was picked to fill Kang's slot at the foreign ministry, while Ri Yong-ho, Kim's deputy in the talks, was named a vice-foreign minister.

Power transfer

The ruling party conference "for electing its supreme leadership body will take place in Pyongyang on September 28", the KCNA said on Tuesday.

A similar congress held in 1980 confirmed Kim, the North Korean leader, as successor to his father Kim Il-sung, who died in 1994.

The conference, initially scheduled for early September and postponed without any explanation, is expected to put a new leadership line-up in place, spell out possible policy shifts and give top party posts to Jong-un's supporters.

Kim, 68, reportedly suffered a stroke in August 2008 and has visibly aged since then. Some reports say he also has kidney problems that require dialysis.

In 2005, the US, China, South Korea, Russia and Japan reached a new disarmament pact with North Korea.

A 1994 deal with the US had collapsed in 2002 when Washington accused Pyongyang of running a secret uranium enrichment programme.

In 2009, North Korea quit the disarmament-for-aid talks, and then conducted a nuclear test that drew tightened UN sanctions.