His remarks, in the East Room at the White House, came following weeks of criticism by fretful Democrats in Congress concerned that the rollout of the exchanges Oct. 1 may hurt them in the 2014 midterm elections.
On Oct. 1, individuals, families and small-business owners across the country will be able shop for private insurance online through insurance exchanges. Coverage begins in January, when most Americans must have insurance.
"Once these marketplaces are up and running, no one can be turned away from private insurance plans," Obama said.
Recognizing that there would be "hiccups" along the way, Obama said he was "110 percent committed to getting it done right" and learning along the way.
He cited as an example the first pass of the application that was 21 pages that was reduced to three and the industry standard is 17 pages.
"This is going to be a lot of work," Obama said. "There still is a lot of political bickering over this law."
Obama also outlined the Affordable Care Act's popular provisions -- already in effect -- such as allowing children to remain on parents' insurance plans through age 26 and requiring insurance companies to cover people with pre-existing conditions.
He also urged people to get the facts about the law and its impacts.
"Don't be bamboozled," he said.
About half of Americans say they still don't understand what the 2010 act actually provides, an April survey by the non-partisan Henry J. Kaiser Family Foundation found, with 4-in-10 Americans unaware the act is still the law of the land.
Health and Human Service Secretary Kathleen Sebelius and other officials will travel the country to promote enrollment this summer as part of a larger public education campaign, the secretary said.
Meanwhile, House Speaker John Boehner, R-Ohio, said he would schedule another vote to repeal ACA for next week. The act has survived nearly 40 such votes so far.