Reversing an earlier pledge to not lay off state workers before Jan. 1, Gov. David A. Paterson said on Thursday that he would dismiss government employees before the end of this year to close a persistent budget gap.

“We’re going to have to,” he said, speaking at a forum in Manhattan.

Mr. Paterson offered no more details, saying he was uncertain how many workers would be laid off or when.

But Mr. Paterson delivered a blistering denunciation of state employee union leaders for their refusal to compromise on their bargaining agreements.

He cited a successful legal challenge by unions to block his plan to furlough half the state’s work force in criticizing union leaders for failing to grant “the slightest concession” to produce about $250 million in savings he has been seeking from government workers.

“They should hang their heads in shame,” he said.

Speaking at a forum sponsored by The Wall Street Journal and interviewed afterward, Mr. Paterson said that state employees were not retiring voluntarily fast enough to generate sufficient savings.

Last year, in exchange for an agreement to reduce the state’s long-term pension costs, Mr. Paterson signed in a memorandum of understanding with public employee unions that he would not lay off any state workers during his term, which expires Dec. 31.

In June, the Paterson administration began preparing for layoffs, but the expectation was that they would not take effect at least until Jan. 1. He hinted then, though, that they might have to be imposed earlier.

“’I don’t think the memorandum of understanding is one that could not be changed because of events not within the contemplation of the parties,” Mr. Paterson said at that time. “Everybody was saying that the economy would change by the third quarter of 2009. That didn’t happen. And so that’s why we’re placed in the position that we are now. Obviously, if the situation got worse, we would look at perhaps speeding up the plan and challenging the memorandum of understanding.”’

Darcy Wells, a spokeswoman for the state’s Public Employees Federation, said the union would “take whatever measures we have to” to ensure that Mr. Paterson abides by his agreement with state workers.

The fact that retirements have lagged, she said, “is evidence that the early retirement incentive wasn’t implemented very well and we had warned about that from the beginning.”

Mr. Paterson has said he is not trying to coerce workers into grantinc concessions. “I would like everyone in the public to get the message that our economy is in peril,” Mr. Paterson said in June, “that our state ran out of money in December for the first time in history.”