Geneva - North Korean Foreign Minister Ri Su Yong said on Tuesday that his country had the power to deter an "ever-increasing nuclear threat" by the United States with a pre-emptive strike if necessary.
His rare speech at the UN-backed Conference on Disarmament drew a rebuke from the US ambassador Robert Wood who urged Pyongyang to stop making threats and rid itself of nuclear weapons.
Ri said joint military exercises being staged by South Korea and the United States were "unprecedentedly provocative in nature and have an especially high possibility of sparking off a war."
"The DPRK [Democratic People's Republic of Korea] cannot but bolster its nuclear deterrent capability to cope with the ever-increasing nuclear threat of the US. Now the DPRK has the power of deterring the US and conducting a pre-emptive strike as well, if necessary," Ri told the Geneva forum.
North Korea fired two short-range missiles off its eastern coast on Monday, South Korean officials said, in a move seen as a defiant response to this year's US-South Korean military exercises. Pyongyang regularly denounces the annual drills, which it views as a preparation for war.
The missiles landed in the sea between the Korean Peninsula and southern Japan early on Monday morning after travelling for about 490km, according to South Korea's Defence Ministry.
Ri, speaking in Korean, did not refer to the firing, but said the divided Korean Peninsula was a "touch-and-go nuclear powder-keg".
Takashi Uto, Japan's parliamentary vice-minister for foreign affairs telling the forum the missile firing was a "clear violation" of UN Security Council resolutions.
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US envoy Wood told the conference the exercises with South Korea, held for almost 40 years, were "transparent and defence-oriented" and in full compliance with the armistice ending the 1950-53 Korean War.
"We call on the DPRK to immediately cease all threats, reduce tensions and take the necessary steps towards denuclearisation needed to resume credible negotiations," Wood said, referring to six-party talks that collapsed in 2008.
"Let me be clear. We will not accept North Korea as a nuclear-armed state and we will do what is necessary to defend ourselves and our allies," Wood added.
Ri, striking a conciliatory note, noted that North Korean leader Kim Jong Un had underscored in his New Year's address that the North and South should achieve great national unity.
"The DPRK will not spare its sincere efforts to bring about great change in inter-Korean relations this year," Ri said.