UNITED NATIONS The tiny Pacific nation of the Marshall Islands is persisting with an unprecedented lawsuit demanding that the United States meet its obligations toward getting rid of its nuclear weapons. It filed notice Thursday that it will appeal a federal judge's decision to dismiss the case.

The island group was the site of 67 nuclear tests by the U.S. over a 12-year period after World War II, with lasting health and environmental impacts, including more than 250 people exposed to high amounts of radiation.

The Marshall Islands filed its lawsuit last year, naming President Barack Obama, the departments and secretaries of defense and energy and the National Nuclear Security Administration. Obama in 2009 called for "a world without nuclear weapons" and said the U.S. would take concrete steps toward that goal, a declaration highlighted by the committee that awarded him the Nobel Peace Prize months later.

The U.S. is a party to the Nuclear Nonproliferation Treaty, a landmark agreement to stop the spread of nuclear weapons. The United Nations this month will host the treaty's latest five-year review conference.

But the Marshall Islands claims the U.S. is modernizing its nuclear arsenal instead of negotiating in good faith on disarmament, as the treaty requires. The lawsuit seeks action on disarming, not compensation.

A federal judge in San Francisco last month granted the U.S. government's motion to dismiss the lawsuit, saying the Marshall Islands didn't have standing to bring the case.

"Requiring the court to delve into and then monitor United States policies and decisions with regard to its nuclear programs and arsenal is an untenable request far beyond the purview of the federal courts," the judge's order said. It added that the authority to negotiate with foreign countries falls under the government's executive branch, not the judicial one.

The Marshall Islands says the executive branch is the very one that has neglected its disarmament obligations for years.

"We believe the district court erred in dismissing the case," the lead attorney for the Marshall Islands, Laurie Ashton, said in a statement announcing the appeal in the San Francisco-based 9th U.S. Circuit Court of Appeals. "The Marshall Islands, like every party to the NPT, is entitled to the United States' fulfillment of its NPT promise."

The statement also said the nuclear threat is "now magnified by the deteriorating relationship between Russia and the U.S., which between them control over 90 percent of the world's nuclear weapons."

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Marshall Islands to appeal in nuclear case vs. US; says US is modernizing arsenal, not cutting