The United States and South Korea have reaffirmed their commitment to South Korea's defense in the face of an expected North Korean rocket launch.

South Korean officials say Defense Minister Kim Kwan-jin discussed the launch with his American counterpart Leon Panetta by telephone Tuesday morning. Both sides say the officials agreed the launch is a “serious provocation” and that they will coordinate efforts to monitor the launch.

ON Monday, U.S. State Department spokeswoman Victoria Nuland said the launch will serve only to further isolate North Korea's communist government.

“North Korea's launch of a missile would be highly provocative, it would pose a threat to regional security, and it will be inconsistent with its recent undertakings to refrain from any kind of long-range missile launches. And, as you know, we consider that it would be a violation of U.N. Security Council Resolution 1718 and 1874. So we are continuing to make the point that it is a bad idea to do this.”

Pyongyang has announced plans to fire the rocket as early as this week, saying its purpose is to launch a weather satellite into orbit. However the United States and South Korea see the launch as a means of testing a ballistic missile that could be used to deliver nuclear warheads.

U.S. Ambassador to the United Nations Susan Rice said Monday the launch would be a blatant violation of Security Council resolutions which prohibit North Korea from firing any kind of ballistic missile. She said she expects the council to meet in response to any launch and respond in a “credible fashion.”

New evidence has also emerged that North Korea is preparing for what would be its third underground nuclear weapons test.

South Korean intelligence photos, provided Monday to VOA and other news organizations, show new signs of tunneling at the site of the two previous tests, and mounds of earth that could be used to refill the tunnel — one of the last steps before a test.

On Sunday, North Korean space officials took the rare step of allowing foreign journalists to see the rocket that is reportedly being prepared for launch.

Reporters said all three stages of the Unha-3 rocket are on the launch pad at the new Tongchang-ri space facility in North Phyongan province on the west coast.

The launch plan has upended more than a year of painstaking diplomacy aimed at achieving a resumption of six-nation talks aimed at negotiating an end to North Korea's nuclear and missile programs in exchange for needed international aid.

Even China, the North's closest ally, has shown signs of exasperation over the launch plan. Some analysts believe that prompted Beijing's decision last week to allow several North Korean defectors to travel to South Korea after being trapped for almost three years at a diplomatic mission in Beijing.