Rendell spokesman Gary Tuma did not dispute the $600 million figure, and added that the governor is "optimistic" the money will be approved.
"The governor thinks the chances look better now than they have been over the last few weeks," Tuma said.
The money is to cover the state's Medicaid expenditures - that is, health coverage for Pennsylvanians living in poverty, whose ranks have been swelled by the recession.
In July, Rendell and the legislature approved a $28 billion budget for the new fiscal year that relied on the federal government kicking in the $850 million.
During budget negotiations, Rendell said he was confident Congress would approve the funds. But soon after, hopes were dashed when Congress scrapped a bill that would have sent a combined $1.4 billion to help states balance their budgets and pay federally mandated Medicaid obligations.
Losing that money entirely, Rendell said, would be "Armageddon." He estimated that as many as 20,000 layoffs - not only state employees but also teachers and municipal workers whose payrolls rely in part on state money - would result. There would also be cuts in state aid for drug, alcohol, and mental-health counseling; domestic-abuse shelters; and myriad other social-service agencies.
On Monday, Pileggi said receiving even 70 percent of the expected $850 million would still necessitate making painful cuts - but not quite as painful.
"It's a smaller problem than $850 [million], but it's still a problem," he said.
Pileggi and other legislative leaders had been scheduled to sit down with Rendell on Monday to draw up a contingency plan in case the $850 million did not materialize.
Instead, with the U.S. Senate poised to act on the funding issue, the negotiators in Harrisburg contented themsleves with a brief conference call and said they will wait until later in the week to craft a Plan B.
Pileggi said that if the state ends up getting roughly $600 million from Washington rather than the hoped-for $850 million, one area likely to be affected is Rendell's signature issue: funding for basic education in public schools. That aid had been increased in this year's budget.
Tuma, the governor's spokesman, pointed out that there was "a whole range of options" for where to make the necessary cuts.
"The governor has said that all areas of the budget where spending is not mandated would be vulnerable, and he included education in that," said Tuma. "But we'll look at different levels of cuts in many different areas."
Contact staff writer Angela Couloumbis at 717-787-5934 or email@example.com.