Japan will not lodge a complaint against the U.S. government for conducting a third experiment using plutonium to test the capabilities of its nuclear arsenal last summer, Chief Cabinet Secretary Osamu Fujimura said Friday.

Like subcritical nuke tests, the new type of experiment did not involve an atomic bomb explosion. It didn't even require explosives or a nuclear test site. Fujimura stressed the experiment was not banned under the Comprehensive Nuclear Test Ban Treaty.

"We have absolutely no intention of filing some sort of complaint or notice," Fujimura said. "We understand that the U.S. conducted the experiment . . . to maintain the safety and capability of its nuclear weapons stockpile."

According to the U.S. National Nuclear Security Association, the test was conducted between July and September at the Sandia National Laboratories in New Mexico. Similar tests were also held in November 2010 and last March.

Fujimura's comments were Japan's first official response to the latest experiment.

Despite his call for a "world without nuclear weapons," President Barack Obama has seen three subcritical tests since taking office in January 2009. Obama won the Nobel Peace Prize in 2009 largely based on this vision and he is likely to face harsh criticism for the experiments.

"We will continue cooperating with the U.S. to aim for President Obama's (vision of) a world without nuclear weapons and would like to lead such discussions in the international community," Fujimura said.

The NNSA report on experiments conducted within the U.S. Stockpile Stewardship Program showed that the latest test used the "Z-machine," the world's strongest X-ray generator and capable of simulating a nuclear explosion of extremely high pressure and temperature.