WASHINGTON (Reuters) - The Pentagon announced on Thursday that it would allow all dependents of U.S. military personnel to leave Japan's Honshu island, potentially with military assistance, amid concerns about radiation from a crippled nuclear plant.

The Pentagon authorization for the voluntary departure of military families follows a similar order issued late on Wednesday by the State Department. Spokesman Colonel Dave Lapan said "thousands" of dependents of U.S. military personnel were eligible to leave with government reimbursement if they flew on commercial airlines.

(Reporting by Phil Stewart; editing by Jackie Frank)