An underwater image shows oil gushing from the broken riser pipe connected to the well 1,500 metres below the water's surface. (BP)

U.S. President Barack Obama has asked Congress to approve new legislation that would provide immediate funding to help clean up the massive oil leak in the Gulf of Mexico.

The package would allow government agencies to continue their response to the leak, emanating from a broken riser pipe 1,500 metres below the water's surface about 80 kilometres off the coast of Louisiana.

It includes:

• Two advances worth up to $100 million US each for the U.S. Coast Guard to underwrite cleanup operations.
• $2 million for the Food and Drug Administration to monitor and respond to the envionmental impacts of the spill on the seafood industry in the Gulf and surrounding areas.
• $29 million for additional inspections, enforcement and studies conducted by the Department of the Interior in its monitoring of offshore drilling.
• $7 million for various environmental studies that improve the government's response to the spill to be conducted by the Environmental Protection Agency and National Oceanic and Atmospheric Administration.

• Increasing allowable per-incident expenditures from the Oil Spill Liability Trust Fund to $1.5 billion from the current $1 billion.

Out-of-work fishermen like these, hoping to be hired to lay oil booms to protect their fishing grounds from oil in Louisiana, could be eligible for financial assistance under the proposed legislation. (Gerald Herbert/Associated Press)The proposed legislation would also allow the government to accelerate support for struggling industries or individuals if BP, which is responsible for the cleanup, "are not paying claims to affected individuals quickly and fairly."

It includes a new unemployment insurance program specifically for those who are out of work because of the spill, providing them with 26 weeks worth of benefits. And it would extend food stamps — known formally as the Supplemental Nutrition Assistance Program — to people affected by the oil spill who would not otherwise have been eligible.

Such steps are necessary to overcome what a White House statement describes as "a massive and potentially unprecedented environmental disaster which can seriously damage the economy and environment of [the] Gulf states and could jeopardize the livelihoods of thousands of Americans."

Almost 17.9 million litres of oil have gushed into the Gulf since the Deepwater Horizon drilling rig, leased by BP, exploded on April 20 and sank two days later.

Despite the government package, BP is ultimately responsible for the cleanup, its costs and paying damages for coastal industries or workers affected economically by the spill.

2nd containment box

BP has been working around the clock to stop the gushing oil well.

The Viking Poseidon lowers the 'top hat' device at the site of the Deepwater Horizon oil spill in the Gulf of Mexico off the coast of Louisiana on Tuesday. (Gerald Herbert/Associated Press)

Late Tuesday, crews began submerging a second containment box into the Gulf of Mexico to try to funnel oil leaking from the underwater well.

The structure, called a "top hat," is a smaller version of the 12-metre tall, 90-tonne box BP tried lowering over the well late last week. That box, which looks something like a giant milk carton, had to be moved aside after a slushy mixture of gas and water clogged the opening in its roof.

A crane lifted the smaller, two-tonne box late Tuesday afternoon from the deck of the Viking Poseidon, one of more than a dozen boats helping the containment effort, and lowered it into the sea about 80 kilometres off the Louisiana coast.

It won't be placed over the spewing well right away because engineers want to make sure everything is configured correctly and avoid the same buildup, BP spokesman Bill Salvin said. Crews also planned to pump in heated water and methanol so ice won't amass. It could be in place by Thursday.

While the cause of the explosion is still under early investigation, it is thought to have begun with a surge of methane gas from deep within the well.

With files from The Associated Press