There are an estimated 450 detainees in Guantanamo Bay detention centre including Australian David Hicks.
Senate Armed Services Committee Chairman John Warner said administration officials have told him the proposed legislation would be submitted after the G8 summit concludes in Russia on July 17.
"I remain on the timetable as outlined to me, that the administration be forthcoming in a formal manner subsequent to the (Group of Eight) conference and their return," Senator Warner said, referring to the bill.
This week, justice department officials lobbied lawmakers to approve an administration framework for emergency tribunals in Guantanamo Bay that was overturned by the Supreme Court on June 29.
The court ruled in part that Mr Bush had exceeded his authority by instituting the military tribunals without Congressional approval.
Senator Warner said it was premature to speculate what type of legislation the administration planned to propose.
"I do not believe we have received the last word about how the administration would like this legislation to proceed," the Republican senator said.
Senator Warner said there was no consensus among lawmakers on whether to approve Mr Bush's initial framework for terror trials should it be presented in legislative form.
"Certainly, there is no consensus here to just rubber-stamp what has been done," said Senator Warner. He said the Senate could start debating the bill in September.
"It is, in my judgment, absolutely imperative that this law be enacted
before Congress completes this Congress" at the end of the year," Senator Warner said.