Online marketplaces at the heart of the health law opened for business Tuesday, often haltingly, as Web-based insurance portals were swamped with consumers who were frequently unable to sign up.

The Obama administration declared the launch a success even as it declined to furnish short-term enrollment numbers in the federally run marketplace for 36 states or a timetable for producing them. 

A snag blocking Web users from signing up was fixed by Tuesday afternoon, said Marilyn Tavenner, head of the federal Centers for Medicare & Medicaid Services. More than 2.8 million visitors came to the federal site after midnight Monday, she said.

Meanwhile, portals operated by Hawaii and Minnesota had not allowed consumers to shop and enroll by late Tuesday afternoon. Maryland's site was greeting visitors with delay notices for much of the day. Washington state's site prompted users to fill out a form and wait for contact by phone. 

"I've tried all morning and I have yet to get on," Emily Nichols, director of operations at The Family Practice & Counseling Network in northwest Philadelphia, told the Philadelphia Inquirer. Nichols was trying to help patients determine their eligibility on the federal site.

Online marketplaces operated by Colorado, Connecticut, California, Kentucky, Vermont, Nevada and Rhode Island appeared to be working.

The Kentucky exchange, Kynect, reported more than 60,000 visitors and more than 1,000 completed insurance applications.

"This surge of early applications demonstrates the pent up demand for quality health coverage for many Kentuckians, who will be able to have that coverage beginning Jan. 1, 2014, because of the ACA," said spokeswoman Gwenda Bond.

President Barack Obama dismissed the problems as glitches typical of software launches.

"Consider that just a couple of weeks ago, Apple rolled out a new mobile operating system and within days they found a glitch, so they fixed it," he said Tuesday afternoon. "I don't remember anybody suggesting Apple should stop selling iPhones or iPads or threatening to shut down the company if they didn't."

Republicans suggested exchange bumps were emblematic of the larger law that the House has now voted more than 40 times to cancel, defund or dismantle.