You can`t without lowering your credit scores.
If you signed a loan and can`t hold up your end,
it will affect your credit.
That being said,
its better to take the hit to your credit on a mod then a foreclosure.
A very good place to start is http://www.makinghomeaffordable.gov
Through this government site,
you can try to modify your loan and lower the payment to 31% of your gross monthly income.
The lender can lower your interest rate as low as 2%,
extend your term to a 40 year,
and/or lower your balance.
Its up to the lender to help you qualify for this program.
If lowering your rate to 2% doesn`t get you down under 31% of your gross income....
they may not approve the mod.
Start with that site and Good Luck!