The U.S. government pressured energy giant BP to avert an environmental disaster as a huge, unchecked oil spill reached coastal Louisiana, imperiling fish and shrimp breeding grounds and vulnerable wetlands teeming with wildlife.

With oil gushing unchecked from a ruptured deepwater well in the Gulf of Mexico off Louisiana, President Barack Obama’s administration piled pressure on London-based BP Plc, the owner of the blown-out well, to do more to shut off the flow and contain the spreading slick.