Marshall Islands is suing the US and eight other nuclear-armed nations over a failure to disarm.
Marshall Islands is suing the United States and eight other nuclear-armed countries, accusing them of failing them in their obligation to negotiate nuclear disarmament.
It accused all nine nuclear-armed states of "flagrant violation of international law" for failing to pursue the negotiations required by the 1968 Nuclear Non-Proliferation Treaty (NPT).
The Pacific nation was the scene of massive US nuclear tests in the 1940's and 1950's; almost 70 nuclear bombs were tested after the Second World War.
It filed one suit specifically directed against the US, in the Federal District Court in San Francisco, while others against all nine countries were lodged at the International Court of Justice in The Hague, a statement from an anti-nuclear group backing the suits said.
The action was supported by South African Nobel Prize winner Archbishop Desmond Tutu, the Nuclear Age Peace Foundation said.
"The failure of these nuclear-armed countries to uphold important commitments and respect the law makes the world a more dangerous place," its statement quoted Mr Tutu as saying.
"We must ask why these leaders continue to break their promises and put their citizens and the world at risk of horrific devastation. This is one of the most fundamental moral and legal questions of our time."
The Nuclear Age Peace Foundation is a US-based non-partisan advocacy group working with Marshall Islands and its international pro-bono legal team.