N.J. Stat. § 20:3-6
Whenever any condemnor shall have determined to acquire property pursuant to law, including public property already devoted to public purpose, but cannot acquire title thereto or possession thereof by agreement with a prospective condemnee, whether by reason of disagreement concerning the compensation to be paid or for any other cause, the condemnation of such property and the compensation to be paid therefor, and to whom payable, and all matters incidental thereto and arising therefrom shall be governed, ascertained and paid by and in the manner provided by this act; provided, however, that no action to condemn shall be instituted unless the condemnor is unable to acquire such title or possession through bona fide negotiations with the prospective condemnee, which negotiations shall include an offer in writing by the condemnor to the prospective condemnee holding the title of record to the property being condemned, setting forth the property and interest therein to be acquired, the compensation offered to be paid and a reasonable disclosure of the manner in which the amount of such offered compensation has been calculated, and such other matters as may be required by the rules. Prior to such offer the taking agency shall appraise said property and the owner shall be given an opportunity to accompany the appraiser during inspection of the property. Such offer shall be served by certified mail. In no event shall such offer be less than the taking agency's approved appraisal of the fair market value of such property. A rejection of said offer or failure to accept the same within the period fixed in written offer, which shall in no case be less than 14 days from the mailing of the offer, shall be conclusive proof of the inability of the condemnor to acquire the property or possession thereof through negotiations. When the holder of the title is unknown, resides out of the State, or for other good cause, the court may dispense with the necessity of such negotiations. Neither the offer nor the refusal thereof shall be evidential in the determination of compensation.
N.J.S. § 20:3-6