NEW YORK, FEB. 17 -- The New York Post's management and unions began "critical" round-the-clock talks today in a last-ditch bid to work out a deal before Rupert Murdoch's Friday deadline to close the 187-year-old newspaper.

But Jerry Cronin, the president of the key drivers' union, refused to participate in the negotiations because of the newspaper's unwillingness to put his offer of overtime cutbacks on the bargaining table.

Despite Cronin's absence, other union leaders, appearing tense but resolute, described the meetings as pivotal.

"It's critical, it's very critical," said pressman's union president Lenny Higgins. "If Murdoch stays with a Friday deadline and he doesn't move that position, it's going to be impossible" to save the newspaper.

The Post, founded by Alexander Hamilton in 1801, is the nation's longest continuously published daily newspaper.

Murdoch told the tabloid's unions on Feb. 8 that he would permanently stop the presses at 2 p.m. Friday unless they agree to $24 million in salary and staff cutbacks.

Murdoch's sale of the financially ailing Post to real estate developer Peter Kalikow is contingent on the unions' acceptance of the cuts.

But while the Post seems to have softened its position somewhat, allowing the unions to determine how the cuts would be allocated, union negotiators took a grim view of management's stance at the talks and did not expect an early settlement.

"They are negotiating within limits," said labor lawyer and mediator Theodore Kheel, who is advising the unions. "Like Henry Ford said, 'You can have any color car you want, as long as it's black.' The unions can have any cost reductions as long as they add up to $24 million."

Cronin spent the morning in a separate meeting with Post management, where an arbitrator heard his charge that Murdoch failed to give 30-day notice as required by the drivers union contract when he set the Friday shutdown date.

George McDonald, president of the Allied Printing Trades Council, an umbrella group that includes eight of the nine unions, expressed optimism after the session, saying, "I'm always optimistic."

He said both sides "went over the figures again" during the meeting and said officials were prepared to work round the clock to reach a settlement.

The original cuts demanded by Murdoch include a reduction of 79 jobs at the paper and a 12 percent wage cut spread over three years to achieve the $24 million in savings.

Murdoch was forced to sell the Post because of a federal rule barring cross-ownership of a newspaper and television station in the same market. Murdoch also owns WNYW-TV in New York.

He faces a similar situation in Boston, where he owns the Boston Herald and WFXT-TV.