My company forcing me sign an agrrement for issue of R/E letter.

This query is relating to the issuance of a R/E (Relieving/)Experience certificate from my employer. I was working with a global consulting organization with presence in India in for close to 10 years. I resigned last month and requested my organization to issue me a Experience/ Relieving certificate. When issuing me the certificate, the company wants me to sign a undertaking that I shall not accept any employment from their Customers, failing me they shall not/ delay issuing me the R/E certificate. Can I refuse to sign the undertaking and force them to issue the R/E certificate. Just to smooth matters out, if I sign the undertaking and join a customer, can they take any legal action against me? I am enclosing the draft of the undertaking as below - ============================================== a. Solicitation of Business from Customers Except in the performance of the duties hereunder, Employee shall not, during the term of employment, and for a period of one (1) year following the termination of employment, solicit or accept business, or otherwise provide services, directly or indirectly, for Employee or on behalf of or in conjunction with any other person or business entity, from or to anyone who was a customer of Employer within twelve months prior to the termination of Employee’s employment. b. Acceptance of Employment from Customers Employee shall not, during the term of employment, and for a period of one (1) year following the termination of employment, accept employment from, or provide services to, whether as an employee, partner, shareholder, independent contractor, consultant or otherwise, anyone who was a customer of Employer within twelve months prior to the termination of Employee’s employment. c. Solicitation of Employer’s Employees Employee shall not, during the term of employment, and for a period of one (1) year following the termination of employment, solicit or hire, directly or indirectly, for Employee or on behalf of, or in conjunction with, any other person or business entity, anyone who was an employee of Employer within twelve months prior to the termination of Employee’s employment. The term “solicit” when used anywhere in this Agreement includes calling, contacting, hiring or accepting business from customers or employees of Employer. =========================================== Can you please advise ?