White House spokesman Gordon Johndroe said the United States sees the several short-range guided missiles the North lobbed into the sea that separates it from Japan "as a routine exercise that they do from time to time."

U.S. officials, eager to make progress on a nuclear disarmament accord with the North that has been stalled over a financial dispute, have been hesitant to criticize Pyongyang.

Japanese Prime Minister Shinzo Abe called the tests "extremely regrettable" but said his country does not consider them a serious threat to national security.

At the State Department, deputy spokesman Tom Casey said he did not believe that the tests had any particular implications for the six-party nuclear disarmament process.

"I don't think it causes any fundamental shift in either their ( North Korea's) military posture or anyone else's," he said.

Casey added that the tests have no apparent effect on the moratorium that North Korea has imposed on long-range missile tests.