Non Compete agreement is preventing my ability to work

I am an employee of a company currently working on H1B and my 6 years are over. They are not willing to process my work visa(TN). The client is willing to take me through a different vendor but my company is bringing non-compete agreement in view and saying i should not work though other vendor.

Could some one please clarify whether the employer can enforce the agreement and come after me? If he is not willing to process my other work visa(TN) dont i have any option?