The United States warned North Korea against provocations Tuesday, using a standard linguistic formula to shrug off Pyongyang's threat to scrap the armistice which ended the Korean war.

North Korea's latest saber-rattling came hours before the United States and China made a joint call for tightened sanctions on the isolated state following its third nuclear test on February 12.

"The DPRK will achieve nothing by threats or provocations which will only further isolate North Korea," White House spokesman Jay Carney said, calling Pyongyang's latest threats not new and helpful.

North Korea earlier threatened to scrap the armistice, which dates from 1953, citing US moves to impose sanctions for its nuclear test and tensions over South Korean-US military exercises.

The North's military said it could launch a "precise" strike anytime, unrestrained by the armistice. It also warned it could mount a strike with atomic weapons to counter any US nuclear threat.

In a statement on official media, the military called the joint exercise a "most blatant" provocation and slammed a "vicious" scheme by the US and its allies to push for tougher United Nations sanctions.

The armistice will be "completely" nullified from March 11, when the South Korean-US exercise gets into full swing in the South, the North said.

Kerry urges N. Korea to get back to talks
Doha (AFP) March 5, 2013 - US Secretary of State John Kerry Tuesday urged North Korean leader Kim Jong-Un to "take responsible action for peace" and get back to the negotiating table over Pyongyang's nuclear program.

"Rather than threaten to abrogate, the world would be better served if they (North Korea) would engage in legitimate dialogue and legitimate negotiations," Kerry told reporters as he wrapped up a nine-nation trip.

Kim should "take responsible action for peace and for responsible activity within the region," Kerry said, just hours after Pyongyang threatened to scrap the 1953 armistice which ended the Korean war.

"Our preference is not to brandish threats to each other, it is to get to the table and to negotiate a peaceful resolution to that crisis," he stressed.

But the top US diplomat, who is finishing his first overseas tour since taking over the helm of the US State Department, warned that "we will continue to do as necessary to defend our nation and region together, our allies."

In a separate interview, Kerry told CNN television that it would be very easy for Kim, who took over the leadership of his isolated country just over a year ago, to "prove his good intent here."

"Just don't fire the next missile, don't have the next test. Say you're ready to talk and invite those talks, and people would be prepared to engage in that conversation, I'm convinced," Kerry said.

Six-party talks over North Korea's nuclear program involving the two Koreas, China, the US, Russia and Japan have been stalled since December 2008.

North Korea, which earlier this year launched its third nuclear test, has been in the spotlight again after a visit by former basketball star Dennis Rodman, who has become the most high-profile American to meet the young leader.

But Kerry dismissed Rodman's insistence that he was engaged in "basketball diplomacy" telling NBC television: "Dennis Rodman was a great basketball player, and as a diplomat, he was a great basketball player."

North Korea earlier threatened to scrap the armistice, which dates from 1953, citing US moves to impose sanctions for its nuclear test and tensions over South Korean-US military exercises.