Leaders of the Pennsylvania Convention Center Authority set a deadline of a minute before midnight Monday for trade unions representing workers at the Philadelphia center to agree to new work rules allowing exhibitors to do more of their own work on shows at the center.

"We have anticipated and are preparing for a range of outcomes, but prefer a cooperative path," wrote center Chairman Gregory J. Fox, President John J. McNichol, and Bob McClintock, chief operating officer of facilities manager SMG, in an open letter Monday.

They added that last week's brief strike by Carpenters Local 8 against the center created "far-reaching and quantifiable" damage to the center's business and has resulted in competitors trying to take shows away from Philadelphia. The ultimatum is the Center's response.

- Joseph N. DiStefano