SEOUL, March 28 (Reuters) - The United States flew two Stealth bomber practice runs over South Korea on Thursday, in a second show of force to North Korea after a B52 bomber made a similar run earlier this week amid rising tensions on the Korean peninsula.
The flights came after North Korea said it would attack American bases in the Pacific following a U.S.-led drive to impose sanctions on North Korea for its third nuclear weapons test.
The North has also threatened U.S. "puppet" South Korea with war and the U.S. mainland with nuclear attack.
"This mission by two B-2 Spirit bombers assigned to 509th Bomb Wing...demonstrates the United States' ability to conduct long-range, precision strikes quickly and at will," the United States Forces in Korea said in a statement.
North Korea has put its armed forces on readiness to fight what is says are "hostile" war drills by the United States and South Korea. The U.S. says the annual drills are defensive.
Pyongyang has also cancelled an armistice agreement with the United States that ended the 1950-53 Korean War and cut all communications hotlines with U.S. forces, the United Nations and South Korea.
The U.S. military said that its bombers had flown more than 6,500 miles to stage a trial bombing raid from their bases in Missouri as part of Foal Eagle war drills being held with South Korea.
The U.S. military announced on March 15 it was bolstering missile defences in response to threats from the North, including a threat to conduct a preemptive nuclear strike against the United States.
Despite the shrill words, few believe North Korea, formally known as the Democratic People's Republic of Korea, will risk starting a full-out war.
North and South Korea are still technically at war anyway after their 1950-53 civil conflict ended with the armistice, not a treaty.
North Korea conducted a third nuclear weapons test in February in breach of U.N. sanctions and despite warnings from China, its one major diplomatic ally.
Despite the tide of hostile rhetoric from Pyongyang, it has kept a joint economic zone with the South open as it generates $2 billion a year in trade from the venture, money the impoverished state can ill-afford to lose.
North Korea will celebrate the anniversary of the birth of its founding father, Kim Il-sung, on April 15. The current ruler is Kim Jong-un, his 30-year old grandson.
While the North has an armoury of Soviet-era Scud missiles that can hit South Korea, its longer-range missiles remain untested.
Independent assessments of its missile strike force suggest that it may have the theoretical capacity to hit U.S. bases in Japan and Guam, but the North has not tested these missiles.
North Korea shelled a South Korean island in 2010 and is charged with the sinking of a South Korean naval vessel in the same year. Pyongyang denies it sank the ship.