Beverly D. Mackereth, secretary of the Department of Public Welfare, said it was not that any specific piece of the proposal was being rejected, but that Pennsylvania officials were concerned about the tone of a phone conference call with federal officials this week.
"Maybe we heard negatives after we always had the impression they would approve," said Mackereth, who did not participate in the call.
An HHS spokesman declined to address the specifics of the conversation, saying only that talks continue between officials with the Center for Medicaid and Medicare Services (CMS) and the Corbett administration.
"CMS remains in close contact with the state during the waiver-application public-comment period and continues to provide technical assistance before making a decision," said agency spokesman Fabien Levy.
Corbett had submitted his "Healthy PA" proposal to the department in February. He is seeking a waiver to impose job-search requirements and require premiums for an additional 500,000 potential Medicaid recipients while reducing benefits and cutting services - including chiropractic care, podiatry, optometry and some transportation - for the 2.2 million already in the program.
Under the plan, Pennsylvania would use federal Medicaid dollars to pay for private insurance for those making less than 138 percent of the poverty level - $16,105 for an individual in 2014, $32,913 for a household of four.
Earlier this month, Corbett retreated somewhat on the provision that applicants be required to search for jobs, suggesting in a letter to HHS Secretary Kathleen Sebelius that he would like to turn that requirement into "a voluntary, one-year pilot program to positively encourage those who are able to work" by reducing premiums.
Corbett had said he wants to have the program in place by Jan. 1, 2015. Had his administration accepted Medicaid expansion as 25 other states have done, individuals could have begun receiving insurance in January.
The federal government is paying 100 percent of Medicaid expansion costs through 2016 - the first three years of the program - and no less than 90 percent after that point. Corbett has argued the program still would be too costly after 2016.
As attorney general, Corbett joined with more than two dozen other Republican attorneys general and governors who sued to block the Affordable Care Act.
When he took office in 2011, Corbett resisted Medicaid expansion, but then offered his own plan last September that would require a federal waiver to proceed.
Two states, Iowa and Arkansas, have so far received federal approval for private-market alternatives to the Affordable Care Act's Medicaid expansion. Corbett's similar concept would go further.
A 30-day federal public comment period on the proposal ends at 6 a.m. April 11.