Deepwater Horizon blowout preventer 'faulty'
Oil industry chiefs say it is too early to conclude what caused the disaster.
A climate change bill just submitted to the Senate could allow states to veto some offshore drilling plans.
Meanwhile, President Barack Obama has also proposed new legislation which foresees $188m (£127m) in emergency funding to cope with the fallout from the oil spill. His administration intends to recover most of the money from BP.
In a letter to House speaker Nancy Pelosi, Mr Obama requested $100m in immediate funding for the Coast Guard and $29m for the Secretary of the Interior for additional inspections, enforcement and studies, saying he would "spare no effort to clean up whatever damage has been caused".