Seoul, South Korea ? North Korea’s massive stockpile of chemical weapons is as threatening as its nuclear program, analysts said Thursday, highlighting an aspect of the secretive regime’s pursuit of weapons of mass destruction that is rarely talked about.

Adding to already high tensions in the region, a Japanese report said North Korea may fire its most advanced ballistic missile toward Hawaii around Independence Day — the day when the regime test-fired a long-range missile three years ago, though it failed seconds after liftoff.

Pyongyang’s missile and nuclear programs are centerpieces of the regime’s catalog of weapons of mass destruction.

But the impoverished nation, which has put most of its scarce resources into boosting its military capabilities under its “army-first” policy, also has a large chemical arsenal, as well as capabilities to produce biological weapons.

On Thursday, an international security think tank warned that these weapons are no less serious a threat to the region than the North’s nuclear arsenal.

The independent International Crisis Group said the North is believed to have between 2,500 and 5,000 tons of chemical weapons, including mustard gas, phosgene, blood agents and sarin. These weapons can be delivered with ballistic missiles and long-range artillery and are “sufficient to inflict massive civilian casualties on South Korea.”

“If progress is made on rolling back Pyongyang’s nuclear ambitions, there could be opportunities to construct a cooperative diplomatic solution for chemical weapons and the suspected biological weapons program,” the think tank said in a report.

It also called on the U.S. to engage the North in dialogue to defuse the nuclear crisis, saying “diplomacy is the least bad option.” It said Washington should be prepared to send a high-level special envoy to Pyongyang to resolve the tension.

South Korea’s annual defense report, published early this year, said that in addition to chemical weapons, the North is believed to be capable of producing biological weapons with agents like anthrax and smallpox.

But of immediate concern is Pyongyang’s ballistic missile program, which would get a major boost if it is able to fire the Taepodong-2, which was last tested on July 4, 2006. That missile fell into the water about 40 seconds after takeoff.

Disregarding the setback, North Korea conducted its first-ever atomic test blast three months later.

On Tuesday, President Barack Obama and South Korean President Lee Myung-bak met in Washington and agreed to build a regional and global “strategic alliance” to persuade North Korea to dismantle all its nuclear weapons.

In a rare move, leaders of Russia and China used their meetings in Moscow on Wednesday to urge the North to return to nuclear talks and expressed “serious concerns” about tension on the Korean peninsula.

The joint appeal appeared to be a signal that Moscow and Beijing are growing impatient with Pyongyang’s stubbornness. Northeastern China and Russia’s Far East both border North Korea, and Pyongyang’s unpredictable actions have raised concern in both countries.