Ryan, during an expected marathon markup session on his budget proposal for fiscal year 2012, said the country was on a downward spiral if it doesn't make tough, hard cuts now.
The $5.8 trillion in spending cuts -- such as changing federal payments to Medicaid programs to a block grant to the states and shifting Medicare to the private sector -- his budget proposal would make over the next decade would be "gradual" but cannot be avoided, Ryan told Democratic critics.
Other areas targeted for cuts or revamps include education grants, environmental projects, food stamps, transportation spending, government salaries, and corporate and personal taxes.
In his opening remarks, Ryan noted opponents would attack his proposal as hurting Americans.
"Nothing will hurt the American people more than staying with the status quo," he said.
His proposal is "more than a budget, it is a cause" to help get America out of debt, he said.
"We can't keep spending money we don't have," he said. "We have to address the problem and spending is the problem."
If nothing is done, he said, today's children would face the prospect of not having as much as their parents and future generations would be financially strapped.
Rep. Chris Van Hollen of Maryland, the ranking Democrat on the budget panel, attacked the proposal, saying it recognizes individual self-reliance but does not recognize America also is about uniting to work for the common good, which often requires government involvement.
"We do not see the government as the enemy but, as the imperfect instrument by which we can accomplish together as a people what no individual or corporation can do alone," he said.
Van Hollen criticized a budget he said cuts aid to seniors and the poor while preserving tax breaks for big business and the super-rich.
"Where is the shared sacrifice?" he said.
We all love America. … The question is how do we keep America strong, dynamic and exceptional," Van Hollen said, and that's where the parties diverge.
"Make no mistake, significant, sustained cuts" must be made, Van Hollen said. "But this budget will take America back."
Rep. Debbie Wasserman Schultz of Florida, selected Tuesday by President Obama to replace outgoing Democratic National Committee Chairman Tim Kaine, called the proposal a "path to poverty" and accused Republicans of "trying to back out on our promise" to care for seniors.
With the proposal being considered, Van Hollen said, Republicans are telling states and vulnerable persons "we're going to take this out of your hide."
For fiscal 2012 the GOP plan would authorize $3.5 trillion in total spending, leaving a budget deficit of just under $1 trillion next year.
The proposal could be considered on the House floor next week.