The United Steel Workers issued a strike notice in case negotiations for a new contract with refiners break down, but the move is a legally required announcement and doesn't necessarily mean a work stoppage is looming at plants that produce almost two-thirds of the nation's motor fuels. The USW and industry representatives could reach an agreement; they could continue negotiating with 24-hour extensions of the current contract; or the two sides could leave the table and the USW goes on strike. Management would have to find ways to keep fuel production going at ExxonMobil, the Total Port Arthur, Valero Energy Port Arthur and Motiva Port Arthur refineries that produce a combined 12 percent of the nation's motor fuels east of the Rocky Mountains.