Faculty union leaders at Hofstra University said Monday that professors have authorized a strike if an agreement is not reached with the college’s administration for a new, five-year contract before the current one expires at midnight Wednesday.

Hofstra officials said Monday night that they are confident an agreement will be reached.

About 725 full-time and part-time professors, members of the college’s chapter of the American Association of University Professors, could begin a job action as early as Thursday, just days before the first day of fall semester classes on Sept. 6.

The private, 10,000-student university will host the first debate between the presidential nominees on Sept. 26, placing the school in the national spotlight.

“The university will gain a lot of visibility — and we are very proud of that — but on September 27th, when the debate is over, we still have to go back to work,” said Dennis W. Mazzocco, AAUP chapter president and a 17-year tenured professor in the Lawrence Herbert School of Communication. “We are just trying to come to common ground.”

On Wednesday, the union membership voted 97 percent in favor of giving its leadership the authority to call the strike, Mazzocco said.

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Hofstra, in its statement Monday, said, “Negotiations between the AAUP and the university are continuing. We’re confident that a mutually agreeable conclusion will be reached this week. The authorization vote is standard operating procedure during a negotiation.”

In 2011, while negotiating the current contract, the AAUP chapter voted to authorize a strike. The faculty and administration reached a tentative agreement on Aug. 30, 2011 — one day before the contract was to expire.

Hofstra, which the nonpartisan Commission on Presidential Debates preselected last year as an alternate debate site, was named to hold the event after Wright State University in Dayton, Ohio, bowed out. The Hempstead university will be the first school to host presidential debates in three consecutive presidential election cycles.

At issue in the negotiations are differences over salaries and promotion schedules, as well as significant changes to the faculty health plan that would substantially increase out-of-pocket expenses, Mazzocco said. Faculty members now contribute 25 percent toward the cost of their health plan.

The professors are asking for a 17 percent raise over the next five years. The administration is offering less than half that, Mazzocco said.

Hofstra officials did not respond to questions about specifics of contract terms under discussion.

The union and university negotiators have met 19 times since they began collective bargaining meetings in February, Mazzocco said. More meetings are scheduled Tuesday and Wednesday in the University Club on the Hempstead campus, he said.

“Frankly, I didn’t think we would be at this point so close to the contract expiration — but here we are,” Mazzocco said. “We are trying our best in bargaining to control the cost of the health care in such a way so it doesn’t eat up the raises.”

Hofstra’s faculty union has gone on strike twice since the chapter formed in 1973. The last such job action occurred in September 1988 and lasted six days.

Professors in the Maurice A. Deane School of Law and the Hofstra Northwell School of Medicine are not represented by the union.