U.S. Agriculture Secretary Mike Johanns said Friday he will press Japan to remove the age limit on imports of U.S. beef, hardening the demand from an earlier call to raise the limit to 30 months from the current 20 months.

Johanns also reiterated that the Department of Agriculture will not allow U.S. meat producers to voluntarily conduct blanket testing on cattle for mad cow disease. He added, however, that it will allow such testing if ordered to do so in an ongoing federal court case.

His remarks underscored a new strategy of urging Japan to adopt U.S. standards for safeguarding against mad cow disease when negotiations on beef trade resume.