China said it would persist with controversial tax rebates to steel exporters to support the sector’s painful restructuring, defying a United States move to impose punitive import duties on Chinese steel products, according to Reuters. A worldwide steel glut has become a major trade irritant, with China under fire from global rivals who say it is dumping cheap exports after a slowdown in demand at home. In a marked escalation of the spat, the United States on Tuesday said it would impose duties of more than 500 percent on Chinese cold-rolled flat steel, widely used for car body panels, appliances and in construction.