Chief administrative officer Harold Curran declined to say why North Slope is pulling out until after the borough assembly meets to discuss the matter next month.
The port authority is a partnership formed 11 years ago by the Fairbanks North Star Borough, the North Slope Borough and the city of Valdez to promote an All-Alaska Gasline.
Port authority officials said the pending withdrawal won't disrupt efforts to truck natural gas to Fairbanks by 2012 or to build a gas pipeline from the North Slope to Valdez.
"Nothing's changed," said Valdez Mayor Bert Cottle, the port authority chairman. "The mission of the port authority has been and still remains to get gas to Alaskans. That hasn't changed whether there's two entities or three entities."
The Fairbanks and North Slope assemblies -- plus the Valdez City Council -- must approve the withdrawal by June 15 before it's final.
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