The White House warned North Korea to refrain from future hostile acts amid indications Pyongyang could soon embark on a new nuclear test or may plan more missile launches.
Pyongyang should "refrain from engaging in any more hostile or provocative actions. They do nothing to advance the cause of peace on the Korean peninsula (or) in Northeast Asia," White House spokesman Jay Carney said.
He said such hostile acts would "do nothing to help the North Korean people, many of whom are starving because of the predilection of the North Korean regime to spend money on weapons systems rather than on economic development."
Carney's comments came amid new speculation that North Korea could soon conduct a third nuclear test, possibly within two weeks, after firing a long-range rocket this month.
South Korea's Chosun Ilbo newspaper reported on preparations for a test in the northeastern town of Punggye-ri, where the North carried out two previous nuclear blasts in 2006 and 2009.
A South Korean government official told AFP on April 8 on condition of anonymity that satellite images showed a new underground tunnel built at the nuclear test site besides two others where the previous tests were conducted.
US Defense Secretary Leon Panetta also cautioned Pyongyang, saying during a visit to Brazil on Tuesday that even through the rocket launch was a failure, it still amounted to a "provocation."
"We strongly urge North Korea not to engage... in any dangerous provocation that would provide instability," Panetta told reporters in Brasilia.
On Monday, Carney had condemned bellicose North Korean behavior after Pyongyang's military threatened to turn parts of Seoul to "ashes."
North Korea had warned of retaliation after the United States scrapped a deal for food aid over the rocket launch earlier this month by Pyongyang, the failure of which was an embarrassment for the regime of new leader Kim Jong-Un.
Obama visited the demilitarized zone between the two Koreas last month and denounced the isolated and impoverished state as a nation which cannot make "anything of any use" and "doesn't work."