A federal judge has rejected the US military's request to dismiss a legal challenge to its plans for two Marianas islands, Pagan and Tinian.
The plans to use the islands as live-fire and bombing sites are linked to a proposed transfer of 5000 US marines to neighbouring Guam from Japan.
The lawsuit was filed by the NGO Earthjustice on behalf of Marianas citizen groups, who believe the plans will devastate their islands.
Earthjustice's attorney David Henkin said US law required the military to be open about all impacts of its plans.
"What the law requires is the navy be honest and forthright with the American people about what all of the impacts would be associated with moving five thousand marines to Guam, including the devastation associated with the live-fire training," said Mr Henkin.
"We are hopeful that once all that information is out on the table, that the navy would have second thoughts about its plans and would make changes as they have in the past" he said.
"You know, if the court agrees with us that the failure to disclose these impacts before making the decision to move the marines to Guam violated the law, as we believe it did, we hope the court will order the navy to do a new environmental review that fully reveals all the impacts."