WASHINGTON (Yonhap) -- In a rare public message for North Korea's new leader, Secretary of State Hillary Clinton on Thursday urged "this young man" to choose between continued dictatorship and a "transformative" leadership.

"This young man, should he make a choice that would help bring North Korea into the 21st century, could go down in history as a transformative leader or he can continue the model of the past," Clinton said.

She was having a joint press availability with Defense Secretary Leon Panetta and South Korea's foreign and defense ministers -- Kim Sung-hwan and Kim Kwan-jin.

It marked the second "two-plus-two" session of the top diplomats and defense officials from the allies. The first one was held two years ago in Seoul.

The international community had both hopes and doubts over the North's leader, Kim Jong-un, reportedly in his late 20s. He took over power half a year ago after the sudden death of his father, Kim Jong-il, who ruled the communist nation for 17 years.

The Kim Jong-un regime first showed signs of active engagement with the U.S., producing a Feb. 29 deal on some good-will steps, including the suspension some of its nuclear activities.

But the North frustrated and angered the world with a long-range missile launch in April.

Clinton stressed that Pyongyang will "achieve nothing by threats or provocations, which will only continue to isolate the country and provide no real opportunity for engagement and work toward a better future."

Korea's foreign minister said the allies have reaffirmed the need to deal sternly with the North's military provocations.

"We agreed that, should North Korea provoke again, then that we will show a very decisive response," he said.

He added, however, the road to dialogue remains open if Pyongyang changes its attitude, not just words but action.

Such a warning and overture for the North is not new. But Seoul's defense chief noted the timing.

"Today's two-plus-two ministerial meeting was held at a strategically critical moment amid the continuing provocation and threats from North Korea and volatile security environment in North Korea, a time which calls for a proactive alliance response," he said.

He added the allies will bolster cooperation to counter cyber-threats from North Korea.

A joint statement issued earlier also read, "To this end, they decided to establish a cyber issues dialogue involving relevant ministries and agencies, which will help coordinate our government, military, and commercial security policies."

Meanwhile, Panetta said a deal is expected to be reached soon on Seoul's push to extend the range of its ballistic missiles.

"I think we are making good progress, and our hope is that we can arrive at an agreeable solution soon," he said without elaborating.