; and (B) is recognizing the labor organization as the exclusive representative of the employees in such unit who perform or will perform such work for the purposes of collective bargaining pursuant to section 9 of the National Labor Relations Act ( 29 U.S.C. 159 ). (3) Certification If a dispute over majority status or the appropriateness of the unit described in paragraph (2) arises between the employer and the labor organization, either party may request that the National Labor Relations Board investigate and resolve the dispute. If the Board finds that a majority of the employees in a unit appropriate for purposes of collective bargaining who perform or will perform work funded under this section has signed valid authorizations designating the labor organization as their bargaining representative and that no other individual or labor organization is currently certified or recognized as the exclusive representative of any of the employees in the unit who perform or will perform such work pursuant to the National Labor Relations Act, the Board shall not direct an election but shall certify the labor organization as the representative described in section 9(a) of the National Labor Relations Act ( 29 U.S.C. 159(a) ) with respect to such employees. (4) Commencement of collective bargaining Not later than 10 days after an employer receiving funding under this section receives a written request for collective bargaining from a recognized or certified labor organization representing employees who perform or will perform work funded under this section, or within such period as the parties agree upon, the labor organization and employer shall meet and commence to bargain collectively and shall make every reasonable effort to conclude and sign a collective bargaining agreement. (5) Mediation If the parties have failed to reach an agreement before the date that is 90 days after the date on which bargaining is commenced under paragraph (4), or any later date agreed upon by both parties, either party may notify the