Stephen Hadley

Speaking on Fox News Sunday, National Security Adviser Stephen Hadley warned North Korea against conducting a nuclear test.

"If there is a nuclear test, obviously, that would be a defiance by North Korea of every member of the six-party talks, including China," he said.

The six-party talks bring together the United States, North Korea, China, South Korea, Japan and Russia. They began in August, 2003 but stalled last year after North Korea refused to return to the negotiating table.

Japan recently called for the North Korean issue to be referred to the U.N. Security Council, for possible sanctions. This position runs counter to Chinese comments last week that Beijing does not want to use sanctions to pressure Pyongyang.

Mr. Hadley acknowledged some differences of opinion among the five nations negotiating with North Korea. But he added that all the countries, including China, are, in his words, "on the same page."

"I think the important thing is that the top level of the government, there is agreement that there must not be a nuclear North Korea," said Mr. Hadley. "And there is a strategy that we are moving forward to put pressure on North Korea."

The National Security Adviser did not specify what steps the United States will take, but he added that Washington has been and will continue putting what he called "a lot of diplomatic pressure" on Pyongyang.