The worst oil spill in U.S. history hits its 40th day on Saturday with Gulf residents clinging to one tenuous hope: that BP’s complicated “top kill” operation will plug the gushing well.

Beleaguered Louisiana residents heard from President Barack Obama and BP CEO Tony Hayward on separate visits to the Gulf coast on Friday as they tried to get a handle on a crisis damaging the credibility of both the government and BP.

Obama, facing criticism that he responded too slowly to the environmental catastrophe in the Gulf of Mexico, assured Louisianians during his five-hour visit that they “will not be left behind” and that the “buck stops” with him.

Hayward, on a visit to the site of the April 20 rig explosion that killed 11 workers and unleashed the oil, said the energy giant needed up to two more days to determine if the top kill will stop the underwater gusher once and for all.