The United States says a rocket launch or future nuclear test by North Korea would only isolate its communist government further.

U.S. State Department spokeswoman Victoria Nuland made the comments Tuesday as South Korean intelligence photos, obtained by VOA, showed what appear to be preparations for a third North Korean nuclear test.

Nuland said she was not in a position to confirm whether the North is preparing for another nuclear test, in addition to a long-range rocket launch planned for this month. She urged China to use its influence with North Korea to persuade it to not go ahead with a rocket launch.

Pyongyang maintains that the rocket, to be launched between April 12 and 16, will carry only a weather satellite, but the U.S. and South Korea say the event is a test of a ballistic missile.

North Korean space officials took the rare step Sunday of allowing foreign journalists, including one from VOA , to see the rocket. Reporters said all three stages of the Unha-3 rocket were on the launch pad at the new Tongchang-ri space facility in North Phyongan province on the west coast.

Jang Myong Jin, general manager of the launch site, said that under the Space Treaty, every country has the right to develop space technology for peaceful purposes.

“The United States-sponsored United Nations Security Council resolution did talk about the technology of ballistic missile launches. However, there is a more important treaty than this resolution and that is the Space Treaty. The Space Treaty clearly states that every country has the right to develop space technology and explore space for peaceful purposes.”

Responding to a question from VOA, Jang Myong Jin dismissed criticism that North Korea is developing technology in spite of severe food shortages in the country.

“No matter how much we starve, don't we have to innovate and better develop technology?”

South Korean Defense Ministry spokesman Kim Min-seok said at a news conference in Seoul that his government sees the launch as a provocation.

“We want to clarify that it (the launch) is a provocation that threatens the peace and stability of the Korean peninsula and northeast Asia. We (the South Korean military) are fully prepared to protect the South Korean people and respond firmly against any acts of provocation (by North Korea) that threaten the peace and stability of the Korean peninsula.”

China's Foreign Minister Yang Jiechi acknowledged that Beijing — Pyongyang's most important ally — is troubled by the launch plan. At a press conference after talks Sunday with his Japanese and South Korean counterparts, he called for more diplomacy.

“We considered and exchanged views about the situation on the Korean peninsula, including the announcement by the DPRK (Democratic People's Republic of Korea) that they plan to launch a satellite. The Chinese side once again pressed our point. The China side is troubled by the developments, and strongly encourages everyone involved on all sides, at high and low levels, to remain calm and reasonable. These issues need to be worked out in a diplomatic and peaceful manner.”

VOA meanwhile has obtained South Korean intelligence photos showing that North Korea appears to be preparing for a third nuclear weapons test.

An accompanying intelligence document, first disclosed Sunday by Yonhap news agency, says the images show workers digging a new tunnel at the Punggye-ri nuclear test site in the northeast. The North conducted two previous nuclear tests in tunnels at the site — first in October 2006 and again in May 2009.

The report says it appears the tunnel work is in its final stage.

North Korea agreed in February to stop nuclear tests, uranium enrichment and long-range missile launches. At the same time, U.S. Secretary of State Hillary Clinton announced U.S. plans to provide the impoverished North with more food aid. That aid was canceled following the announcement of this week's rocket launch.

The United States, China, Russia, South Korea and Japan have jointly negotiated with the North to end its nuclear program. But those talks broke down in late 2009, when Pyongyang expelled international inspectors and then conducted its second nuclear test.