(Adds details throughout, Medicaid backlog numbers and fresh quotes from Sebelius and Menendez)
By David Morgan
WASHINGTON, April 10 (Reuters) - More than 7.5 million people are expected to sign up for private health coverage this year under President Barack Obama's healthcare law, the top U.S. health official said on Thursday.
The number, which surpasses the 7.1 million total Obama announced just last week, includes 400,000 people allowed to sign up for private health plans through a federal marketplace after a March 31 deadline because they had not been able to complete their enrollment applications on time.
"We expect that to continue to grow," said U.S. Health and Human Services Secretary Kathleen Sebelius, who released the latest figures during testimony before the Senate Finance Committee.
Sebelius said traffic on HealthCare.gov, the federal enrollment website for consumers in 36 states, surged to 4.8 million visitors on March 31. A federal call center received 2 million calls on that day. Fourteen state-run marketplaces also experienced a surge and are expected to add to the federal data.
Republicans have criticized the government for not providing more detailed data on how many people have actually completed enrollment by paying their first month's premium. Individual insurers have estimated that number at 80 percent to 85 percent of their new members.
"It's like Amazon.com taking stock of how many people have placed items in their shopping carts and then counting them as sales. In other words, it's a false metric," said Republican Senator Orrin Hatch of Utah.
Obama's Patient Protection and Affordable Care Act aims to expand health coverage to millions more Americans through subsidized private insurance on state marketplaces and through an expansion of the Medicaid program for the poor.
Sebelius acknowledged there are extensive backlogs of people in some U.S. states who have applied for Medicaid but remain unable to access care because of out-of-date state computer systems. Last week, the government said three million people had enrolled in Medicaid from Oct. 1 through Feb. 28.
Obamacare enrollment has become a political football as Republicans and Democrats battle for control of Congress in November's congressional elections. Democrats say the unexpectedly high numbers illustrate the demand for healthcare reform, while Republicans contend the figures are inflated by people whose existing policies were canceled because of Obamacare's consumer standards.
Since Oct. 1, a total of 11.7 million have qualified for Medicaid, which is provided jointly by federal and state governments. The numbers include people who gained coverage through the Obamacare expansion and others who enrolled in Medicaid programs that pre-date the healthcare law. About half of the 50 U.S. states are expanding Medicaid.
Sebelius said an untold number of Medicaid applicants are stuck in states that did not install computer programs capable of transferring data to the federal government's automated system, as the law intended.
"We are actually kind of ramping up the pressure on states and will look at some potentially administrative reductions in payment if people don't pick up this pace," Sebelius said, without providing details.
The Medicaid issue was raised by Democratic Senator Robert Menendez, who said a single county in his home state of New Jersey is reported to have a backlog of 10,000 applicants and only six state workers to process the applications by hand. New Jersey is among the states that expanded Medicaid.
"It would take nearly a year and a half to clear the backlog," Menendez added. (Reporting by David Morgan; Editing by Michele Gershberg, Chris Reese and Andre Grenon)