Assembly members are due to debate the controversial bill brought by Social Development Minister Mervyn Storey next Tuesday.
In a statement, the first minister said the stakes could not be higher.
However, Sinn Féin has again accused the DUP of scaremongering with its budget forecasts.
Sinn Féin's Daithi McKay said Finance Minister Arlene Foster should appear before her Stormont committee to explain her prediction that the Stormont budget could be cut by £2.8bn.
The BBC has seen a document which Mrs Foster circulated to other executive ministers.
In it, she said no deal on welfare would mean the executive having to make cuts of £604m in order to balance its books.
Mrs Foster said health could lose £280m and education £114m.
Talks are continuing at Stormont about the welfare deadlock.
The SDLP is understood to be holding internal discussions over whether its MLAs should sign a petition of concern which could block the welfare reform bill.
The Northern Ireland parties had agreed a deal on Westminster's welfare reform in the Stormont House Agreement last December.
However, Sinn Féin withdrew its support for the bill in March.
Peter Robinson has said the assembly could not survive the scenario which would unfold if the welfare reform bill is not approved.