<p><br /> A giant oil slick from a deadly offshore drilling rig explosion could hit the fragile US Gulf Coast shoreline by Saturday.<br /> </p><p><br /> The leak has a circumference of about 600 miles which is slightly bigger than the American state of West Virginia.<br /> </p><p><br /> "The wind will nudge the oil slick more to the north-northwest," said Dan Kottlowski, senior meteorologist at AccuWeather. "It might make it onshore over the southeast Louisiana coast first, and later threaten beaches in Mississippi, Alabama and Florida," Kottlowski said.<br /> </p><p><br /> The Coast Guard is using eight underwater robots to try to activate a cutoff valve on the ocean floor to stop the oil flow.<br /> </p><p><br /> The leak may also be set alight where it is bubbling to the surface above the well to try to stop the spread.<br /> </p><p><br /> The Swiss-based Transocean Ltd's Deepwater Horizon sank on April 22, two days after it exploded and caught fire.<br /> </p><p><br /> The White House and Congress have launched separate probes in the worst offshore incident in nearly a decade.<br /> </p><p><br /> The infamous Exxon Valdez disaster spilled about 11 million gallons of oil into the Prince William Sound in Alaska, when it ran aground in 1989.<br /> </p>
