North Korea has begun preparations for the ruling party's congress slated for May, picking candidates for provincial delegates, a source said Tuesday.

The Workers' Party of Korea plans to hold its first party congress in 36 years in May, where North Korean leader Kim Jong-un will likely unveil new lines of policies. Seoul's spy agency said that the event is expected to be held on May 7.

A source familiar with North Korean affairs said the country started the process to select candidates for delegates at counties and cities for the event in mid-March.

"Given past records, a list of representatives for the party congress may come out by mid-April," the source said.

Around 3,000 delegates are expected to join the days-long party congress to be held in Pyongyang, it said.

North Korea's state media has yet to publicly comment on details over its preparation for the event. Seoul's unification ministry declined to confirm the North's move.

The party congress is likely to serve as a key event that will reveal the North Korean leader's policy direction in his fifth year in power. Kim inherited power following the sudden death of his father Kim Jong-il in late 2011. 

It will mark the first party congress since October 1980, as well as the first since Kim took power.

Former North Korean leader Kim Jong-il advocated a military-first, or "songun," policy by operating the National Defense Commission as the main decision-making body.

But the young leader has shifted his focus to the party while pursuing his signature policy of developing nuclear weapons and boosting its moribund economy in tandem, commonly known as the "byeongjin" policy.

Seoul and Washington have warned that the North's dual-track policy is a dead end.

In the past, the North made key political decisions or unveiled policies at its party congress. Also, it had major reshuffles in the party's leadership.

"North Korea may seek to carry out a shift in generations in the party's leadership at the May congress," said a ministry official.

As the North faces tougher U.N. sanctions and unilateral punitive actions by major countries, it won't produce tangible accomplishments on the economic front, analysts said.

In early March, the United Nations Security Council slapped the strongest sanctions on the North in decades over its January nuclear test and long-range rocket launch in February.

Analysts said that the planned party congress may be held during a shorter period of time, given that there would be few countries which will send their delegates to North Korea due to its latest provocations.

"The party conference is likely to proceed for three to five days, mostly with local delegates," said Cheong Seong-chang, a senior researcher at the Sejong Institute.

He said that the North's leader is expected to unveil his vision for governance over the next 10 years, reaffirming his dual pursuit of economic growth and nuclear weapons development. (Yonhap)