WASHINGTON (AP) — A bipartisan immigration bill soon to be introduced in the Senate could exclude hundreds of thousands of immigrants here illegally from ever becoming U.S. citizens, according to a Senate aide with knowledge of the proposals.

The bill would bar anyone who arrived in the U.S. after Dec. 31, 2011, from applying for legal status and ultimately citizenship, according to the aide, who was not authorized to discuss the proposals before they were made public and spoke on condition of anonymity.

It also would require applicants to document that they were in the country before Dec. 31, 2011, have a clean criminal record and show enough employment or financial stability that they're likely to stay off welfare.

Those requirements could exclude hundreds of thousands of the 11 million immigrants in the U.S. illegally from the path to citizenship envisioned by the bill, the aide said.

Although illegal immigration to the U.S. has been dropping, many tens of thousands still arrive each year, so the cutoff date alone could exclude a large number of people. That may come as a disappointment to immigrant rights groups that had been hoping that anyone here as of the date of enactment of the bill could be able to become eligible for citizenship.

But Republicans in the immigration negotiating group had sought strict criteria on legal enforcement and border security as the price for their support for a path to citizenship, which is still opposed by some as amnesty. Details on the criminal record requirement were still being finalize,d but anyone with a felony conviction was likely to be excluded, the aide said.

The new details emerged as negotiators reached agreement on all the major elements of the sweeping legislation.

After months of closed-door negotiations, the "Gang of Eight" senators, equally divided between the two parties, had no issues left to resolve in person, and no more negotiating sessions were planned. Remaining details were left to aides, who were at work completing drafts of the bill.

"All issues that rise to the member level have been dealt with," Sen. Chuck Schumer, D-N.Y., said in a statement Thursday. "All that is left is the drafting."

Democratic Sen. Dick Durbin of Illinois said the bill probably would be introduced on Tuesday.

The landmark legislation would overhaul legal immigration programs, require all employers to verify the legal status of their workers, greatly boost border security and put millions of immigrants living in the U.S. illegally on a 13-year path to citizenship. A top second-term priority for President Barack Obama, it would enact the biggest changes to U.S. immigration law in more than a quarter-century.

Deals gelled over the past two days on a new farm-worker program and visas for high-tech workers, eliminating the final substantive disputes on the legislation.

Next will come the uncertain public phase as voters and other lawmakers get a look at the measure. Already, some conservatives have made it clear their opposition will be fierce.

Sen. Jeff Sessions, R-Ala., complained that the bill would ensure that millions get amnesty but border enforcement never happens.

"This is also why it is so troubling that (Senate Judiciary Chairman Patrick Leahy, D-Vt.) has rejected the GOP request for multiple hearings and that members of the Gang of Eight have publicly announced their intention to oppose any amendments," Sessions said in a statement Thursday. "To proceed along these lines is tantamount to an admission that the bill is not workable and will not withstand public scrutiny."

Pro-immigrant activists also were gearing up for a fight even as they expressed optimism that this time, Congress will succeed in passing an immigration overhaul bill. Many of those pushing for the legislation were involved in the last major immigration fight, in 2007, when a bill came close on the Senate floor but ultimately failed.

"I think it's a pretty remarkable breakthrough that eight ideologically diverse senators are working so well together on such a challenging issue," said Frank Sharry, executive director of America's Voice, a group advocating for an overhaul of U.S. immigration policy. "And I think the fact that they've come up with a bill they can all support and defend suggests that it's the heart of a bill that will finally pass into law."

Once the legislation is introduced, it will be considered by the Senate Judiciary Committee, which has scheduled a hearing for Wednesday and likely will begin to amend and vote on the bill the week of May 6. From there, the bill would move to the Senate floor.

Both in committee and on the floor, the bill could change in unpredictable ways as senators try to amend it from the left and the right. The Gang of Eight — Schumer, Durbin, and Sens. John McCain and Jeff Flake, R-Ariz., Marco Rubio, R-Fla., Lindsey Graham, R-S.C., Robert Menendez, D-N.J., and Michael Bennet, D-Colo. — have discussed banding together to defeat amendments that could significantly alter the legislation.

Even more uncertain, though, is the Republican-led House, where a bipartisan group is also crafting an immigration bill, though timing of its release is uncertain. Many conservatives in the House remain opposed to citizenship for immigrants who have been living in the U.S. illegally.