Government office refused to give no objection letter

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Hi,

My friend's father is applying for visit visa and he is a Govt employee(Currently on payroll). He has planned to visit USA for 3 months, as his daughter is in USA and two unmarried sons are in India. His office sanctioned his leave, but refused to sign on no objection letter as it is a very long process. Please advise, what to do now? He has got all other supporting documents as mentioned in this site.