The Senate plans to open debate Monday on the bill and consider amendments throughout next week. Majority Leader Harry Reid, D-Nev., has set a Memorial Day deadline for completing the measure, but it's unlikely the complex plan can be finished that quickly.
Democratic leaders are waiting for the Senate to pass a bill before they consider one in the more-polarized House. They plan to act on immigration in July, but Speaker Nancy Pelosi, D-Calif., has told President Bush she won't bring up a bill unless he can promise at least 70 Republicans will support it.
If the House passes a version, House and Senate negotiators would have to blend the two bills into one. The House and Senate then would each have to pass that product. It would then go to Bush for his signature.
Bush has said he's eager to sign the measure into law by August, when Congress adjourns for four weeks, returning Sept. 4.