The program would require action from a Republican-dominated Congress. "With no details or information on the cost, this seems more like a talking point than a plan," said Cory Fritz, a spokesman for House Speaker John Boehner, R-Ohio.
The White House said details on the cost and funding would come in the State of the Union Address Jan. 20 and the president's budget request Feb. 2. But the White House expects 9 million students to participate, and save them up to $3,800 a year. That would place the cost at $34.2 billion, though there are questions about building capacity at the nation's 1,100 community colleges.
The federal government would pay three quarters of the cost, at least initially.
In some ways, the community college plan is a bookend to Obama's 2013 proposal to pay for universal pre-Kindergarten through a state and federal partnership. That proposal, which relied on dwindling tobacco tax money to provide federal matching funds, never got traction in Congress.
But Cecilia Munoz, Obama's domestic policy adviser, said Obama's pre-K proposal spurred state and local governments to increase the number and quality of pre-school offerings, and hopes the college proposal will do the same. "We don't expect the country to be transformed overnight, but we do expect the conversation to begin tomorrow," she said.
Obama, joined by Vice President Joe Biden, will announce the plan at Pellissippi Community College in Knoxville. Obama's plan is modeled after the Tennessee Promise -- a state-level free-college plan starting this fall, paid for with Tennessee Lottery proceeds.
That plan, Munoz noted, has support from Republican lawmakers in Tennessee.
Munoz said the college plan would require the cooperation of states, community colleges and students. States would have to pick up a quarter of the cost -- more or less depending on how much they currently fund community colleges.
"Community colleges have to raise their game by establishing standards to allow students to transfer those credits to a four year degree," she said. "And students must take responsibility for their education, earn good grades and stay on track to graduate in order to earn free tuition."
The America's College Promise program would be available to traditional and non-traditional college students, she said, and would support those seeking the first two years of a bachelor's degree, an associate's degree, or even just job training.
Obama said a world-class education starts with children, but that adults need training, too. "It's not just for kids, we also have to make sure that everybody has the opportunity to constantly train themselves for better jobs, better wages, better benefits."