LOS ANGELES/NEW YORK, Sept 25 (Reuters) - U.S. companies that rely on East and Gulf Coast seaports have been importing early, shifting goods to the West Coast, and even putting cargo on pricey flights to hedge against a threatened Oct. 1 strike that could jam supply chains and reignite inflation ahead of the U.S. presidential election.

As a strike looms, port operators said labor leaders were refusing to bargain, as big retailers brace for supply chain hiccups.

The union, which represents dockworkers across 36 ports on the U.S. East Coast and the Gulf of Mexico, threatens to strike on Oct. 1. If its members walk off the job at ports stretching from Maine to Texas,