North Korea is not likely to conduct another nuclear test anytime soon, a U.S. institute said Friday, citing recent satellite images that showed ongoing construction work at the only known nuclear test site in the reclusive country.

   The assessment by 38 North, a website by the U.S. Korea Institute of Johns Hopkins University, comes as recent satellite images showed construction work underway to build new a tunnel at the nuclear test site that can be used to detonate another fissile device. The U.S. institute said that construction is still under way and that it may take several months to complete.

   Punggye-ri in Kilju Country on the country's east coast has been used to test three nuclear devices from 2006 onwards. The latest experiment was conducted in February, causing the international community to condemn the North and tighten sanctions.

   The think tanks under the Johns Hopkins School of Advanced International Studies said judging by the amount of unearthed soil from the digging process, the tunnel may already be 500 meters long.

   Experts have said such tunnels need to be at least a kilometer in length for an atomic test to be conducted safely.

   International interest toward Pyongyang's nuclear program has gained momentum after the recent political upheaval in the North involving the leader's uncle has spurred speculation that the communist country may stir trouble again.

   Related to possible provocations by the North, the National Bureau of Asian Research predicted that there is a risk that the isolationist country may conduct another nuclear test, launch a long-range missile or even trigger low-intensity conflict with South Korea in 2014.

   The U.S. institute said the North will be the single largest threat to the Asia-Pacific region in the new year.

   In particular, the NBR said the North may act in an erratic manner and that further nuclear test may highlight the country's ability to refine its knowhow in this field.

   It moreover said the country's young leader Kim Jong-un may trigger confrontation with the South to win the loyalty of hardliners in the military amid the political shakeup. (Yonhap News)