It has also emerged as perhaps the greatest challenge facing those trying to reshape the way health care is delivered in America.
Spending on health care reached $2.2 trillion in 2007 and is expected to increase by more than 6 percent a year, on average, over the next decade, faster than the economy's growth in general, according to the federal Centers for Medicare and Medicaid Services.
Obama's plan would build on the current system in which employers, government and individuals share responsibility for paying the cost and care is delivered privately. The government would play a stronger role by subsidizing coverage for many more people and spelling out stronger consumer protections.
In their letter, the groups estimate that they could slow the annual growth rate by an average of 1.5 percentage points over the next decade, although savings probably would vary in each individual year.
That could potentially mean enormous savings to the economy and to the federal government, a point highlighted Sunday by senior administration officials.
"Health-care costs will continue to rise," said one official, who was not authorized to speak for attribution. "But achieving a slowdown in the rate at which they increase would be a huge accomplishment in terms of freeing up resources for other priorities and in terms of relieving pressure on the federal budget."
In addition to its rosy fiscal promise, the letter also comes at an important political moment for the president and his allies.
Congressional Democrats are intensifying their efforts to develop health care legislation in the face of gathering opposition from conservatives warning of a drift toward government-run health care.
Republican lawmakers last week received a briefing from an influential GOP political strategist about how to challenge the administration's health-care initiative, raising concerns among some Democrats on Capitol Hill.
Sunday, administration officials were quick to hail the letter, calling it a "game changer" that illustrated the momentum behind the president's health-care campaign.
The letter also drew praise from AARP public policy director John Rother, a veteran of past health-care overhaul efforts.
"While serious questions remain about the details, AARP believes the agreement of providers to slow the skyrocketing cost of health care is critical for the health reform we are all working toward," Rother said in a statement.
"Reducing the skyrocketing cost of health care is the only way to create a health-care system that works for all Americans. After all, what good is access to a system that we can't afford?"
The Associated Press contributed to this article.
