Description: The US Government says it won't take over oil clean-up operations in the Gulf of Mexico from BP. Washington had criticised the oil giant for being too slow in its crisis management efforts. BP is pinning its hopes of stopping the gusher on yet another technique never tested 1500 metres underwater: a 'top kill' in which heavy mud and cement would be shot into the blown-out well to plug it up. At least 23 million litres of crude oil have spewed into the Gulf, according to a Coast Guard and BP, though some scientists say they believe the spill has already surpassed the 42 million litre 1989 Exxon Valdez oil spill off Alaska as the worst in US history.