North Korea's young leader Kim Jong-un is set to hold talks with the visiting Mongolian president this week, a South Korean diplomatic source said Monday, in what would be his debut on the summit diplomacy stage since becoming the North's leader.

Mongolian President Tsakhia Elbegdorj arrived in Pyongyang earlier in the day, marking the first visit by a head of state to North Korea since Kim took power in late 2011 upon the death of his father, Kim Jong-il.

"We have been informed that First Secretary Kim and the Mongolian president were scheduled to hold talks today or tomorrow," the diplomatic source in Beijing said.

The source, who spoke on the condition of anonymity, declined to elaborate on the agenda of Elbegdorj's talks with Kim, but Mongolia "hopes to play a role as a constructive arbitrator with regard to the issue on the Korean Peninsula."

Kim, who is believed to be in his late 20s, has been tightening his grip on power and conducted his country's third nuclear test in February of this year, drawing condemnation and sanctions from the international community, including China.

North Korea is becoming increasingly isolated within the international community as it continues to defy international warnings against its nuclear and missile programs. In April this year, Pyongyang asked Ulaanbaatar for food aid.

"North Korea appears to be trying to diversify its diplomatic front as it faces increasing isolation," the source said.

Last week, China's Xinhua news agency reported that Indonesian President Susilo Bambang Yudhoyono sent a personal letter to Kim, expressing hope that friendly cooperation between the two countries will be further developed.

The letter was delivered when the North's ceremonial head of state, Kim Yong-nam, met with visiting Indonesian Foreign Minister Marty Matalegawato in Pyongyang, according to the report. (Yonhap News)