SEOUL, Korea, Republic Of - Facing mounting international pressure over its nuclear and missile ambitions, North Korea has set a date for its biggest political convention in decades next month that is expected to bolster young dictator Kim Jong Un's grip on power.

The ruling Workers' Party, led by Kim, decided Tuesday to open its 7th congress in Pyongyang on May 6, the official Korean Central News Agency reported Wednesday.

It will be the first time the congress, the highest-level decision-making party organ, will be held since 1980, when Kim's late dictator father Kim Jong Il was awarded a slew of top jobs in a confirmation that he was in line to succeed his father, North Korea founder Kim Il Sung.

Since taking power upon the death of his father in late 2011, Kim Jong Un has been struggling to revive his country's troubled economy and grapple with international standoffs over his country's nuclear and missile programs.

The standoff deepened earlier this year when North Korea conducted a fourth nuclear test and a long-range rocket launch, which led to the UN slapping its toughest sanctions on North Korea in 20 years. South Korea and the United States also made their ongoing springtime military drills the largest ever.

In response, Kim last month ordered tests of a nuclear warhead and ballistic missiles capable of carrying warheads. That sparked outside speculation that North Korea could perform a fifth nuclear test ahead of the political convention to burnish his image as a stronger leader fighting hard against foreign aggressions.

South Korean President Park Geun-hye said last week that the North was believed to have completed preparations for a new atomic bomb test. Park warned that such a move would result in stronger sanctions and pressures that would speed up North Korea's collapse.

The North's state media did not say what would be discussed and decided on during the congress. A previous KCNA report said the North decided to hold the convention as the country was faced with "the heavy yet sacred task" of building a "thriving" nation.

South Korean analysts say Kim will likely use the convention as a chance to reshuffle top officials, reveal policy directions and further strengthen his authoritarian leadership.

Kim has orchestrated a series of high-profile executions, purgings and personnel reshuffles in what outside analysts say was an attempt to remove potential rivals or show he's an absolute ruler. Among the executed were his powerful uncle, then the No. 2 in North Korea, and his defence chief. Some experts said repeated bloody power shifts may indicate the young leader has not established the same absolute power that his father and grandfather enjoyed.

The North's state media did not say how long the congress would last. The 1980 convention lasted five days.