(Adds analyst, background on Obamacare)
NEW YORK, Dec 13 (Reuters) - The number of consumers who signed up for 2018 Obamacare health insurance surpassed the 1 million mark in the second-to-last week of enrollment, the government said on Wednesday, but it did not appear to be enough to grow the program.
The Trump administration has worked to undercut former President Barack Obama's national healthcare law by decreasing advertising and discussing ending the mandate that Americans have health insurance, which has weighed on 2018 enrollment.
Through Dec. 9, 4.68 million consumers signed up for the insurance in the 39 states that use the federally run HealthCare.gov website. The deadline for 2018 plans is Dec. 15.
More than 1.07 million consumers selected 2018 Obamacare individual insurance plans in the week ended Dec. 9, a 30 percent increase from the previous week.
Evercore ISI analyst Michael Newshel said last week's acceleration was expected, but was not enough for year-over-year growth.
"With just a few more days left until Fridays deadline, we think enrollment is tracking towards a single-digit percent decline (if renewal rate holds consistent with prior years and year-over-year growth in new sign-ups seen to date is sustained), but it all comes down to an uncertain final surge," Newshel wrote in a research note.
For 2018 to be on track with 2017, 4.52 million people would need to sign up during the week that ends Dec. 15, Newshel said.
The nonpartisan Congressional Budget Office forecast enrollment of 11 million in 2018, a figure that includes HealthCare.gov as well as sign-ups in the 11 states and Washington D.C. that run their own websites and have later deadlines.
An average of 10 million customers had enrolled and paid for Obamacare individual insurance as of Sept. 15, 2017, the U.S. Department of Health and Human Services said on Wednesday, down from 12.2 million who signed up at the beginning of the year. (Reporting by Caroline Humer; Editing by David Gregorio and Andrew Hay)