* Bombastic North Korean threats seem easy to dismiss
* Pyongyang breaks deals, but often makes good on threats
* "Pre-emptive nuclear attack" on U.S. still not possible
By Paul Eckert
WASHINGTON, March 7 (Reuters) - North Korea's blood-curdling war threats are often dismissed as the kind of over-the-top rhetoric the world expects from the reclusive and eccentric leadership in Pyongyang, now in its third generation under Kim Jong-un.
But while the latest threat to launch a "pre-emptive nuclear strike" on the United States is believed by experts to be beyond North Korea's technical capacities, and would be suicidal, history shows there can be bite behind Pyongyang's bark.
"This kind of extreme rhetoric has not been unusual for this regime, unfortunately," State Department spokeswoman Victoria Nuland said on Thursday, adding the United States could defend itself and allies Japan and South Korea in any event.
Asked if the deterrence talk meant that Washington sensed more than bombast, she added, "You have to take a government at its word when it makes these kinds of threats."
Thursday's threat, issued as a statement from North's Foreign Ministry spokesman, came during U.S.-led efforts to pass new U.N. sanctions on North Korea in response to its most recent nuclear test. The Security Council later approved the sanctions.
When it comes to actions welcomed by the United States and its allies, taking Pyongyang at its word is nearly impossible. Twenty years of nuclear diplomacy is littered with broken pledges, dashed deals and a small but growing North Korean nuclear arsenal.
South Korea, likewise, has little to show for hundreds of millions of dollars of aid it sent northward after Seoul and Pyongyang signed a raft of bilateral agreements at their historic June 2001 leaders' summit.
But when it comes to threats of bad behavior, North Korea has a better record of delivering - beginning with the three nuclear tests it carried out in 2006, 2009 and last month in the face of strong international warnings to desist.
The 2009 and 2013 tests defied U.N. sanctions forbidding such tests.
NO 'SEA OF FIRE,' BUT DEADLY ATTACKS
Bruce Klingner, a retired North Korea analyst for the CIA, said Pyongyang, through its Korea Central News Agency mouthpiece, often repeated threats "which are bombastic and seem to indicate impending military attacks that then don't occur."
South Koreans and their financial markets long ago learned to shrug off North Korea's most infamous and lurid threat, to turn Seoul into a "sea of fire."
This week's pre-emptive nuclear attack rhetoric appeared intended to intimidate South Korea, the United States and China, said experts and a U.S. official.
"A lot of it is just their classical reaction to the fact that the international community increasingly is coming together and making it tougher for them to operate - that's the kind of acting out that we often see from North Korea," Glyn Davies, U.S. special representative for North Korea, told a Senate hearing on Thursday.
If the North's aim was to goad Washington back into nuclear talks, it misfired, said Matt Stumpf, Washington director of the Asia Society.
"If North Korea is using new threats to get the United States back to the negotiating table, it is missing how much opinion in Washington, Seoul, Tokyo and Beijing has changed through successive crises," Stumpf said. "This might have been a workable strategy in the past, but there will be little appetite to negotiate until North Korea shows it is committed to real change."
A U.S. Congressional Research Service study published after last month's nuclear test cited intelligence estimates that North Korea had enough separated plutonium for at least half a dozen nuclear weapons.
Carrying out the threat to attack the United States, is not possible, however, without warhead miniaturization, which, the report said, "would likely require additional nuclear and missile tests."
Klingner, now at the conservative Heritage Foundation think tank, warned that "we cannot easily dismiss North Korean threats, because they have often been carried out."
He cited the example of 2010, when after threats against South Korea and vilification of its then-president, Lee Myung-bak, North Korea lashed out in a pair of deadly attacks on a South Korean warship and an island, killing 50 people. North Korea denied responsibility for the ship's sinking.
"The conundrum has always been: Is a new North Korean threat one that will not be carried out, as frequently has been the case in the past, or is it a portent of upcoming action?" said Klingner. (Editing by Warren Strobel and Peter Cooney)