US President Barack Obama on Wednesday defended the centerpiece of his signature health care reform and vowed to fix its widespread technical failures. Speaking at an event in Boston, Obama said he was "not happy" about the health care online marketplace that has been plagued with technical problems for almost a month. "There is no excuse of it," he said. However, he cited the sluggish start of the Massachusetts health care overhaul to explain why people should be patient for the federal health care reform key measure that debuted on Oct. 1. "All the parade of horribles, the worst predictions about health care reform in Massachusetts never came true," said the president. "They are the same arguments that you are hearing now." Obama vowed that he takes "full responsibility" for making sure the current glitches of the online marketplace will get fixed as soon as possible. Earlier Wednesday, U.S. Health and Human Services Secretary Kathleen Sebelius made the apology before lawmakers for the first time for the technical problems of the HealthCare.gov, the online market aiming at getting millions of uninsured or underinsured Americans health care coverage. After its debut on Oct. 1, the website has witnessed high- profile failures and was almost out of service during the first two weeks. Many consumers have reported difficulties of signing up and getting enrolled. While the site has made some improvement recently, the enrollment system is still considered too weak to cope with millions of users who are interested in purchasing health insurance plans.