WASHINGTON, (Reuters) – President Barack Obama said  yesterday his healthcare overhaul needed a public insurance  option to enforce market “discipline,” but stopped short of  saying he would veto legislation without one.

Obama, who has made healthcare reform a top legislative  priority, said he would insist Congress pass a plan to control  skyrocketing costs and cut the number of uninsured. But he  added “we have not drawn lines in the sand” on other issues.

“The public plan, I think, is an important tool to  discipline insurance companies,” Obama told a White House news  conference. “I think there is going to be some healthy debate  about the shape that this takes.”

The United States spends some $2.5 trillion annually on  healthcare, about 16 percent of gross domestic product, but  trails many developed countries on important measures of  health. Some 47 million Americans are uninsured and have little  access to the healthcare system.

Obama, who promised reform during his presidential  campaign, has stepped up his efforts to sell the public on his  proposals, holding a series of speeches and meetings, including  one at the White House set for tonight.

In an interview with ABC’s “Good Morning America” to be  aired today, Obama said he “absolutely” believed  Congress would pass healthcare reform this year because “the  American people understand it has to get done.”