If you can't afford to pay more than your regular payment, you can ask for a Forebearance Plan.  A Forebearance Plan allows your loan to remain delinquent while you continue to make your regular payment or sometimes even less than your regular payment.

Servicers sometimes approve Forbearance Plans if you expect your income to increase in the near future or if they are considering a loan modification but want to make sure you can afford the new payment.