"It's important that North Korea not develop and try to deploy nuclear weapons. That's enormously important," White House spokesman Tony Snow told reporters.

Referring to the warning that a nuclear-armed DPRK would be "unacceptable," Snow said "It's a statement -- no, it's not a lethal threat."

"It's a statement of our policy, which is, we don't think they should have nuclear weapons," Snow said.

The United States has been pursuing diplomatic means to prevent the DPRK from pursuing its nuclear program, the spokesman said.

The DPRK announced Tuesday that it will undertake an unprecedented nuclear test. U.S. Secretary of State Condoleezza Rice said that a nuclear test by the DPRK would be a "very provocative" act.

Pyongyang declared in February 2005 it had nuclear weapons, but there have been no reports of a test.