U.S. government and BP officials are warning that the blown-out oil well causing an environmental disaster on the Gulf Coast may not be stopped until August as the company begins preparations on a new attempt to capture the leaking crude.

The disaster, in its 42nd day on Monday, is already the largest oil spill in U.S. history and officials are calling it the country’s biggest environmental catastrophe.

In the wake of a devastating failure this weekend to plug the BP well with the tricky “top kill” operation, BP Chief Executive Tony Hayward said the Gulf of Mexico leak may not be stopped for two months.