U.N. Secretary-General Ban Ki-moon on Thursday urged a return to talks with North Korea despite its defiant pursuit of nuclear weapons.

Ban, who is on a six-day visit to his native South Korea, made the call during a forum on the southern resort island of Jeju, saying the tensions on the Korean Peninsula are "one of the great challenges to global action and regional cooperation."

"Rising tensions on the Korean Peninsula could cast a shadow across Northeast Asia and beyond," he said in a keynote address at the opening of the Jeju Forum for Peace and Prosperity. "I welcome efforts to move forward, and I stand ready as the secretary-general of the United Nations and also personally to contribute in any way that might be helpful."

Plans by the U.N. chief to visit North Korea last year fell through after Pyongyang abruptly withdrew its invitation.

"We must find the path back to dialogue," Ban said.

Pyongyang has recently made a series of proposals for talks with Seoul, but the South Korean government has rejected them, saying the North is not serious about denuclearization.

"Good relations between the two Koreas are essential for lasting peace not only on the Korean Peninsula but throughout the region," the secretary-general said.

Ban's first visit home in a year has drawn keen attention amid growing speculation he may run for the presidency next year. His second five-year term as U.N. chief ends in December.

On Wednesday, he left open the possibility of a presidential bid, saying he will contemplate his future as a South Korean citizen upon completing his tenure at the U.N.

He also expressed an eagerness to engage with the North, claiming to be the only one to maintain an inter-Korean dialogue channel.

"Even as we keep pressure on the North, there must be efforts to hold talks and ease tensions through humanitarian issues," he said during a meeting with senior journalists Wednesday.

Ban's seeming departure from Seoul's official policy line on Pyongyang has fueled speculation over his presidential ambitions, with observers noting that the former South Korean foreign minister may be building a platform for his future campaign.

Since his arrival Wednesday, the U.N. chief has met with Prime Minister Hwang Kyo-ahn, Unification Minister Hong Yong-pyo and leaders of the ruling Saenuri Party on the forum's sidelines.

On North Korea, Ban was still firm on its nuclear program and human rights record.

"Military spending remains high, while children are wasting.

Human rights are systematically abused," he said. "The authorities of the DPRK must correct these wrongs."

DPRK is the acronym of North Korea's official name, the Democratic People's Republic of Korea.

North Korea was slapped with toughened sanctions in March under a U.N. Security Council resolution adopted in response to its fourth nuclear test in January and long-range rocket launch a month later.

"I encourage the DPRK to cease any further provocations and return to full compliance with international obligations," Ban said.

Urging the international community to "hold on a firm line" on North Korea, he also expressed hope the U.N. resolution's full implementation would lead to the denuclearization of the Korean Peninsula.

After making a short trip to Japan later in the day to attend a G7 summit, Ban will be back late Friday to attend the Rotary International Convention in Goyang, just outside of Seoul, and visit the ruling party stronghold of Gyeongsang to tour a UNESCO-listed folk village and open a U.N. conference.

He is set to return to New York on Monday. (Yonhap)