Thanks for the help

I googled the following info in http://travel.state.gov/passport/get/secondary_evidence/secondary_evidence_4315.html

Foreign Birth Documents + Parent(s) Citizenship Evidence

If you claim citizenship through birth abroad to U.S. citizen parent(s), but cannot submit a Consular Report of Birth Abroad or Certification of Birth, you must submit all of the following:

 Your foreign birth certificate (translated to English)
 Evidence of citizenship of your U.S. citizen parent
 Your parents' marriage certificate
 An statement of your U.S. citizen parent detailing all periods and places of residence or physical presence in the United States and abroad before your birth