Oil prices steadied on Tuesday, helped by a dip in the dollar, but were on track for their biggest monthly drop since March in the face of a global supply glut. A nuclear deal between Iran and the West that is likely to unleash more oil on a market where slowing Chinese growth and a faltering European recovery have eaten into demand and stripped almost 11 percent off the price of crude oil so far in July. Iranian Supreme Leader Ali Khamenei last week vowed to defy American policies in the region, despite the deal over Tehran’s nuclear program, in a speech U.S. Secretary of State John Kerry on Tuesday called “very disturbing”.