SIMI VALLEY, Calif.—The U.S. military's top commanders, groping for ways to cope with a shrinking Pentagon budget, have agreed to a plan that would curb the growth of pay and benefits for housing, education and health—prized features of military life that for years have been spared from cuts.

Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said in a weekend interview that without such changes, the cost of military personnel would soon rise to 60% from about half of the defense budget.

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