North Korea declares itself "proud nuclear power," warns U.S.

I don't want to speculate on hypotheticals. But I do want to give assurances to the American people that the T's are crossed and the I's are dotted.”

— U.S. President Barack Obama

North Korea has boasted of being a "proud nuclear power" and warned the US that it will strike back if attacked.

The statement came after US President Barack Obama said Washington was "fully prepared" for a possible North Korean missile test.

There have been recent warnings in South Korean and Japanese newspapers that the North is preparing another long-range missile launch.

The UN toughened sanctions against the North after a nuclear test on 25 May.

The North has also recently test-fired a number of short-range missiles recently, and in April launched a long-range rocket - which it said was to put a satellite into orbit but which the US said was a missile test.

Military analysts say North Korea's longest-range missile - the Taepodong-2 - has the potential range to reach Hawaii and parts of Alaska.

North Korea warned June 17 of a "thousand-fold" military retaliation against the U.S. and its allies if provoked, the latest threat in a drumbeat of rhetoric in defense of its rogue nuclear program.

Japanese and South Korean news reports said North Korea is preparing an additional site for test-firing a long-range missile capable of striking the U.S.

The warning of a military strike, carried by the North's state media, came hours after President Barack Obama declared North Korea a "grave threat" to the world, and pledged that recent U.N. sanctions on the communist regime will be aggressively enforced.

Obama and South Korean President Lee Myung-bak met in Washington Tuesday for a landmark summit in which the two leaders agreed to build a regional and global "strategic alliance" to persuade North Korea to dismantle all its nuclear weapons.