Reopen deleted line items of PO

Hi,

I need to reopen the deleted line item from my PO.While I do unblock / undelete for particular line item I got error as below,

Requisition XXXXXXX.item 00XXX, created from Production order / network

Message no. 06277

Also when I check in Account assignment tab my PO has got connected with Network.

Can anyone please tell me how to proceed on this issue.

Cheers,

Kumar.S