The Senate proposal says that entire process couldn't start until the borders were fully secure and tracking of people in the U.S. on visas had improved. Those vague requirements would almost certainly make the timeline for achieving citizenship longer than what the White House is proposing.
The president urged lawmakers to avoid making the citizenship pathway so difficult that it would appear out of reach for many illegal immigrants.
"We all agree that these men and women have to earn their way to citizenship," he said. "But for comprehensive immigration reform to work, it must make clear from the outset that there is a pathway to citizenship."
"It won't be a quick process, but it will be a fair process," Obama added.
Another key difference between the White House and Senate proposals is the administration's plan to allow same-sex partners to seek visas under the same rules that govern other family immigration. The Senate principles do not recognize same-sex partners, though Democratic lawmakers have told gay rights groups that they could seek to include that in a final bill.
John McCain of Arizona, who is part of the Senate immigration group, called the issue a "red flag" in an interview Tuesday on "CBS This Morning."
Washington last took up immigration changes in a serious way in 2007, when then-President George W. Bush pressed for an overhaul. The initial efforts had bipartisan support but eventually collapsed in the Senate because of a lack of GOP support.
Cognizant of that failed effort, the White House has readied its own immigration legislation. But officials said Obama will send it to the Hill only if the Senate process stalls.
Most of the recommendations Obama made Tuesday were not new. They were included in the immigration blueprint he released in 2011, but he exerted little political capital to get it passed by Congress, to the disappointment of many Hispanics.
Some of the recommendations in the Senate plan are also pulled from past immigration efforts. The senators involved in formulating the latest proposals, in addition to McCain and Rubio, are Democrats Charles Schumer of New York, Dick Durbin of Illinois, Robert Menendez of New Jersey and Michael Bennet of Colorado, and Republicans Lindsey Graham of South Carolina, and Jeff Flake of Arizona.
Also Tuesday, in another sign of Congress' increased attention to immigration issues, a group of four senators introduced legislation aimed at allowing more high-tech workers into the country, a longtime priority of technology businesses. The bill by Republicans Rubio and Orrin Hatch and Democrats Amy Klobuchar and Chris Coons would increase the number of visas available for high-tech workers, make it easier for them to change jobs once here and for their spouses to work and aim to make it easier for foreigners at U.S. universities to remain here upon graduation.
Julie Pace reported from Washington. Associated Press writer Erica Werner contributed to this report.