UNITED NATIONS (AP) — The U.N. nuclear chief said Thursday that a new nuclear test explosion by North Korea “would be yet another confirmation of a program which is moving full steam ahead in a way that is incredibly concerning.”

Rafael Grossi said the International Atomic Energy Agency sees preparations for a seventh test but has no indication of whether an atomic blast is imminent.

“Everybody is holding its breath,” he told reporters in response to a question. “Further tests, of course, means that they are refining the preparations and the construction of the arsenal. So we are following this very, very closely.”

Grossi added: “We hope it doesn’t happen, but indications unfortunately go in another direction.”

Officials from the United States and its Asian allies Japan and South Korea suspect North Korea is preparing for a nuclear test, and deputy foreign ministers from the three countries said Wednesday their joint response would be “decisive.”

Worries about North Korea’s nuclear program deepened in recent months as the country adopted a new law authorizing the preemptive use of its bombs in certain cases and took reported steps to deploy tactical nuclear weapons along its border with South Korea. This year, North Korea has carried out more than 40 missile launches.

North Korea announced in April 2009 that it was kicking out IAEA inspectors and they have not been allowed to return.