In Singapore where top defense officials from the US, South Korea and Japan have met to discuss the nuclear issue on the Korean peninsula.

U.S. Secretary of Defense Robert Gates, center, shakes hands with Japan's Defense Minister Yasukazu Hamada, left, and South Korea's Defense Minister Lee Sang-hee as they proceed for their trilateral meeting on the sidelines of the Asia Security Summit on Saturday, May 30, 2009 in Singapore. [Wong Maye-E /AP Photo]

They were speaking on the sidelines of an annual security conference with officials from the Asia Pacific region.

Saturday's talks discussed the DPRK's nuclear test, as tensions continue to run high in the Korean peninsula.

Defense chiefs from the three countries pledged a united response.

US defense secretary Robert Gates said the US will not accept the DPRK as a nuclear weapons state and warned against any form of proliferation.

Robert Gates, US defense secretary, said, "The transfer of nuclear weapons or material by North Korea to states or non-state entities would be considered a grave threat to the United Sates and our allies, and we would hold North Korea fully accountable for the consequences of such action."

South Korean Defense Minister said the DPRK's tactic was to use the heightened tensions as a bargaining chip, to secure concessions such as food and other aid.

Lee Sang Hee, South Korean Defense Minister, said, "The DPRK may have mistakenly believed that it could be rewarded for its wrong behavior, but that's no longer the case. We must make the DPRK clearly recognize that it will not be rewarded for its wrong behavior."

The trilateral meeting came as South Korean officials said on Saturday that US spy satellites have spotted signs that the DPRK may be preparing to transport another long-range missile to a test launch site.

In the next few days, regional military leaders and security experts will discuss security issues as well as defense cooperation.

The DPRK's nuclear issue is at the top of the agenda.

(CCTV May 31, 2009)