A bipartisan group of senators known as the “gang of eight,” who are working on a comprehensive immigration reform package for 2013, is hopeful about presenting a bill this week.

The gang of eight announced the reform deal in January, and since then the prospect of a deal has been gaining momentum. The agreement contains a path to citizenship for the approximately 11 million undocumented immigrants in the U.S.

“I think we’re doing very well,” Sen. Chuck Schumer, D-N.Y., said Sunday on CBS’ “Face the Nation.” “We hope that we can have a bipartisan agreement among the eight of us on comprehensive immigration reform by the end of this week.”

Schumer added that great progress has been made over the past two weeks, despite what he called “kerfuffles all along the way.”

“Thus far, we’re on track,” Schumer said, adding that the group will not present a bill until all eight members are in agreement.

One obstacle the others may have to overcome is Sen. Marco Rubio, R-Fla., who could be the key to persuading conservatives to back a bill that would provide citizenship to undocumented people.

When reports circulated last week about an imminent deal, Rubio quickly shut things down, calling the reports “premature.”

Rubio issued a statement, noting that “substantial progress” has been made and that he believes there will be agreement on a measure that modernizes the legal immigration system, improve border security and provide an opportunity for illegal immigrants to seek permanent residency in the future. Such status, according to Rubio, would depend on those immigrants meeting certain criteria.

“That legislation will only be a starting point,” Rubio’s statement read. “We will need a healthy public debate that includes committee hearings and the opportunity for other senators to improve our legislation with their own amendments. … But arriving at a final product will require it to be properly submitted for the American people’s consideration, through the other 92 senators from 43 states that weren’t part of this initial drafting process. In order to succeed, this process cannot be rushed or done in secret.”

Rubio is believed to be a leading 2016 presidential hopeful.

Sen. John McCain, R-Ariz., who was also a guest on the Sunday political-talk show, said the Florida senator has been helping and is an important part of the effort to achieve immigration reform.

McCain said there needs to be a path to citizenship as well as border security, noting that when millions of immigrants were given amnesty in 1986 under the Reagan administration, promises to secure the border failed.

“I’ve got to assure the people of this country and Arizona that we’re not going to have a third wave 10 or 15 or 20 years from now,” McCain said. “Most Americans agree that if you pay back-taxes, if you pay a fine, if you learn English, if you go to the back of the line, then you can and should be eligible for a path to citizenship.”

But some lawmakers are sure to be unhappy with the proposal, McCain later added: “There are entrenched positions on both sides of this issue, as far as business and labor.”