(CNN) -- Citing what it calls U.S. threats to topple its political system, North Korea says it is dropping out of six-party nuclear talks and will "bolster its nuclear weapons arsenal," North Korea's official news agency KCNA reported.
Thursday's report was the first public claim by North Korea to actually possess nuclear weapons.
In the past, Pyongyang has claimed to have the ability and the right to produce them. U.S. officials said in April 2003 that North Korea claimed in private meetings to having at least one nuclear bomb.
U.S. Secretary of State Condoleezza Rice called on North Korea to "reconsider their decision" to withdraw from the talks or risk further isolation, The Associated Press reported.
Rice said the North Koreans, by leaving negotiations, would be "deepening their isolation because everyone in the international community, and most especially North Korea's neighbors, have been very clear that there needs to be no nuclear weapons on the Korean peninsula in order to maintain stability in that region." (Full story)
In the statement reported by KCNA, the North Korean Foreign Ministry said: "We have shown utmost magnanimity and patience for the past four years since the first Bush administration swore in."
"We cannot spend another four years as we did in the past four years and there is no need for us to repeat what we did in those years."
The United States, the two Koreas, China, Japan and Russia have held three rounds of six-party talks since 2003, aimed at persuading the North to abandon its nuclear weapons development in return for economic and diplomatic rewards.
But no significant progress was reported in those talks, all hosted by China, North Korea's last remaining major ally.
A fourth round of talks scheduled for last September did not take place because North Korea refused to attend, citing what it called a "hostile" U.S. policy.
Thursday's statement from the North Korean foreign ministry said the country's nuclear weapons are "for self-defense to cope with the Bush administration's evermore undisguised policy to isolate and stifle the DPRK (Democratic People's Republic of Korea)."
The communist state said it felt "compelled to suspend" participation in the six-nation talks "for an indefinite period."
"We have wanted the six-party talks but we are compelled to suspend our participation in the talks for an indefinite period till we have recognized that there is justification for us to attend the talks and there are ample conditions and atmosphere to expect positive results from the talks," the Foreign Ministry said.
"The U.S. disclosed its attempt to topple the political system in the DPRK at any cost, threatening it with a nuclear stick. This compels us to take a measure to bolster its nuclear weapons arsenal in order to protect the ideology, system, freedom and democracy chosen by the people in the DPRK.
'Axis of evil'
In his inaugural address on January 20, U.S. President George W. Bush did not mention North Korea by name. But he said U.S. efforts have lit "a fire in the minds of men.
"It warms those who feel its power, it burns those who fight its progress and one day this untamed fire of freedom will reach the darkest corners of our world," he said.
In his February 2 State of the Union address, Bush only briefly mentioned North Korea, saying Washington was "working closely with governments in Asia to convince North Korea to abandon its nuclear ambitions."
Bush's tone was in stark contrast to his speech three years ago, when he branded North Korea part of an "axis of evil" with Iran and Iraq. It raised hopes for a positive response from North Korea.
Earlier this month, Bush and South Korean President Roh Moo-hyun agreed to push for an early resumption of the six-nation talks.
But Pyongyang called Bush's call for the spread of freedom in his January 20 inaugural speech as a diabolical U.S. scheme to turn the world into "a sea of war flames."
"In his inauguration speech, Bush trumpeted that 'fire of freedom will reach dark corners of the world.' This is nothing but a plot to engulf the whole world in a sea of war flames and rule it by imposing a freedom based on power," North Korea's state-run Pyongyang Radio said early this month.
Despite pulling out of the six-nation nuclear talks and saying Thursday it will "bolster" its nuclear arsenal, the Foreign Ministry statement said North Korea's "principled stand to solve the issue through dialogue and negotiations and its ultimate goal to denuclearize the Korean Peninsula remain unchanged."
Sohn Jie-ae, CNN's Correspondent in the South Korean capital Seoul, said the possibility of North Korea returning to the talks could not be ruled out.
She said officials from the other countries involved would try to convince North Korea to reverse its decision.