North Korean leader Kim Jong-un, second from left, and North Korean officials attend a launching ceremony for the tactical nuclear attack submarine, Sept. 8. AP-Newsis

North Korea will continue to escalate its nuclear threats against the United States and South Korea next year while seeking to improve its capabilities to strike back with a nuclear weapon if it comes under a nuclear attack, experts said Wednesday.

Jun Bong-geun, a professor emeritus at the state-run Korea National Diplomatic Academy (KNDA), made the point at a briefing on the prospects of international relations for next year, stressing that North Korea has taken the "most aggressive nuclear posture in the world" due to its inadequate "second-strike" capability.

"The nuclear doctrine prevalent among those with second-strike capabilities is 'if you strike me, I will strike back with my nuclear weapons so you will die anyways if you strike me,'" he said.

However, North Korea, with a limited arsenal of only around 50 nuclear weapons, is unlikely to have the capability to launch a nuclear retaliatory attack after sustaining a "first strike" from an adversary, he added.

Pyongyang will seek to increase its number of nuclear weapons to more than 100 "in the shortest possible time," he said.

Choi Woo-seon, a professor at the KNDA, echoed Jun's views, saying North Korea can carry out a provocation any time next year, though it will likely be "limited" under the U.S. extended deterrence.

On growing military cooperation between Russia and North Korea, Jun saw it unlikely for Moscow to transfer arms related to intercontinental ballistic missiles.

"Russia will not do anything to neglect its responsibility at the very least as a permanent member of the U.N. Security Council and a nuclear country under the Non-Proliferation Treaty," he said.

In October, the U.S. government said the North had shipped more than 1,000 containers of military equipment and munitions to Russia.

The revelation came after North Korean leader Kim Jong-un and Russian President Vladimir Putin met at the Vostochny Cosmodrome, a Russian spaceport, in September, raising concerns about a possible arms deal between the two countries. (Yonhap)