The bill is expected to be lengthy and cover numerous issues, including limiting family-based immigration to put a greater emphasis on skills and employment ties instead. McCain and Schumer promised the overhaul would pay for itself, while cautioning that their proposed border security package would be costly.
"Nobody is going to be totally happy with this legislation, no one will be because we have to make compromises," McCain said.
Bennet said the Gang of Eight has agreed to put border security before a path to citizenship, but are opposed to double-sided fences along the length of the U.S.-Mexico border. Some lawmakers in Arizona want more border fences.
"There is not one simple solution to the issue of border security," Bennet said. "This isn't as simple as someone on the East Coast saying 'We need a fence everywhere or we don't.'"
The senators stressed only comprehensive immigration reform, not piecemeal solutions, had any hope of passing both chambers of Congress.
"We are not going to slice it up," McCain said.
The legislation was initially promised in March. Immigration proponents have said the group needs to introduce legislation soon, while some Republican lawmakers complain the process has moved too quickly.
If passed, the legislation could usher in the most sweeping changes in immigration law in nearly 30 years.
Cristina Silva can be reached at http://www.twitter.com/cristymsilva