US Interior Secretary Ken Salazar has promised an overhaul of the agency that regulates offshore oil drilling.
He promised to give more resources and independence to the Minerals Management Service (MMS).
He was making his first appearance before Congress since the April 20 oil spill in the Gulf of Mexico.
Meanwhile, tarballs found off Florida's Key West are being tested to see if they come from the spill. Scientists fear it could travel up the East Coast.
They are increasingly worried that the oil could get caught in a current that could take it to Florida, damaging coral reefs and killing more wildlife there.
The blobs of oil can occur naturally or come from other sources, such as ships.
"We believe it is unlikely (the tarballs) are from the Gulf oil spill, but we'll know for sure in a couple of days. While we are concerned about what will happen, we are trying to keep a positive attitude," Key West Mayor Craig Cates told Reuters news agency.
If they are confirmed as having come from the Louisiana spill, they would mark the farthest point east and south that the leaking oil has reached.
In Washington, Mr Salazar told senators that the US would still have to rely on offshore drilling to meet its energy needs.
"Offshore development is a necessary part of that future," he told a Senate Energy and Natural Resources Committee.
But he promised to give "more tools, more resources, more independence and greater authority" to the Minerals Management Service (MMS), which regulates drilling in the Gulf of Mexico.
A second Senate hearing by the Commerce Committee was also due to question BP America President Lamar McKay and Steven Newman, president of Transocean, which was working on behalf of BP and which owned the rig that exploded, killing 11 people.
Separately, energy giant BP says it is now able to capture the equivalent of 2,000 barrels a day - about 40% - of the oil that is leaking from the ruptured underwater pipe in the Gulf of Mexico. The figure is double the amount reported 24 hours ago.
The oil is being siphoned through a mile-long (1.6km) tube to a tanker on the surface.
BP says it plans to start pumping large amounts of mud into the damaged oil well in an effort to close it altogether.
However, the authorities have expanded the no-fishing zone in the area from 10% to 19% of the US Exclusive Economic Zone in the Gulf of Mexico because of the size of the spill.
Earlier on Tuesday, White House officials were quoted by news agencies as saying that US President Barack Obama would set up a commission to investigate the oil spill.
They said the panel would study oil industry practices, rig safety, regulation and governmental oversight, including the functions of the MMS.
Meanwhile, senior MMS official Chris Oynes said on Monday that he would step down at the end of this month, although no official reasons were given for his resignation.
Mr Oynes has been accused of becoming too close to the industry his agency monitors, the BBC's Madeleine Morris in Washington reports.