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The move follows criticism of the government agency responsible for regulating offshore drilling safety, which Mr. Obama joined last Friday when he denounced the "cozy relationship" between oil companies and federal regulators.

Greenpeace biologist Paul Horsman surveys oil pooled between reeds on the east bank of the Mississippi River's mouth in Louisiana on Monday.

It's not clear who will lead the commission, which could be patterned after past presidential commissions that have investigated incidents such as the 1986 explosion of the Space Shuttle Challenger and the 1979 nuclear accident at Three Mile Island in Pennsylvania. The Challenger commission was led by a former secretary of state, William Rogers, and included a cast of prominent scientists, former astronauts, military officers and engineers. The oil-spill commission won't include any current government employees, a person familiar with the plans said.

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The Coast Guard and the Minerals Management Service (MMS), two agencies that had direct roles in offshore-drilling regulation, have been in the position of investigating their own alleged lapses in connection with the April 20 explosion and fire that sank the Deepwater Horizon oil rig, killed 11 workers and touched off one of the worst offshore oil spills in the U.S. in decades.

Separately, Chris Oynes, the top official overseeing offshore oil drilling for MMS, will retire at the end of the month, according to people familiar with the situation.

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The accident will be the subject of half a dozen congressional hearings this week, including two on Tuesday at which Interior Secretary Ken Salazar is scheduled to testify.

Mr. Salazar, whose department oversees the MMS, said last week he planned to reorganize the agency, splitting the MMS's revenue-collecting officials from those who are supposed to ensure compliance with safety and environmental rules. President Barack Obama last week ordered a review of the MMS, and criticized the "cozy relationship between the oil companies and the federal agency that permits them to drill."

Sen. Joseph Lieberman (I., Conn.), the chairman of the Senate Homeland Security and Governmental Affairs Committee, asked during a hearing Monday why the MMS didn't require BP PLC to have a better plan for dealing with a deep-water blowout such as the one that led to the Gulf spill.

"Until those questions are answered satisfactorily, I don't see how our government can allow any new deep-water wells to be permitted and drilled," Mr. Lieberman said. Officials from the MMS chose not to appear at the hearing, according to Mr. Lieberman.

Mr. Oynes, whose duties include administering the agency's offshore oil and gas program, announced in an email to colleagues Monday that he would leave the agency at the end of the month, according to documents viewed by The Wall Street Journal.

An administration official said Monday, "This was Chris Oynes's decision to retire after almost 35 years of public service. Shortly after the Deepwater Horizon explosion, he approached leadership at MMS and announced he would be retiring on June 30, and today he told his colleagues he would be accelerating his retirement."

A call to Mr. Oynes's office Monday was not returned.

Rep. Nick Rahall (D., W.Va.), chairman of the House Natural Resources Committee, said Mr. Oynes's departure "is one of several steps that will be necessary to fundamentally reform MMS, and it represents an opportunity to begin anew with a clean slate."

A White House spokesman referred questions to the Interior Department.

Separately, Homeland Security Secretary Janet Napolitano told a Senate committee on Monday that responders combating the prolonged BP oil spill in the Gulf of Mexico are still "in the middle of this crisis," and that the effort to stanch the Gulf oil spill are not near an end.

BP, the British oil giant that owns the leaking well, started drilling the first relief well earlier this month to stop the undersea spill, and began work on a second relief well on Sunday. It expects the first to be completed in early August. "Worst-case scenario is we'll be at this for quite a while," Ms. Napolitano said.

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Demonstrators in back hold up signs Monday as BP America Chairman Lamar McKay, right, gets ready to testify before a Senate committee.

She said that thousands of people at the federal, state and local level have been deployed to combat the spill. The Defense Department has approved the activation of up to 17,500 National Guard troops, and more than 1,300 of those are deployed, Ms. Napolitano said.

BP said Monday it hopes to double to 2,000 barrels a day the amount of oil it is siphoning through a pipe inserted into the leaking well during the weekend. BP's estimate is that the well is leaking at a rate of 5,000 barrels a day, but a number of scientists have questioned that figure, saying that the flow could be as much as five times that rate.

Depending on the flow rate, the spill could prove to be the biggest ever in U.S. territory, surpassing the amount of oil released into Alaska's Prince William Sound by the Exxon Valdez in 1989.

Most of the oil has remained offshore, though soft "tar balls" have washed ashore at the South Pass entry to the Mississippi River in Louisiana and Alabama's Dauphin Island. Oil has washed ashore on Louisiana's Chandeleur Islands as well.

—Siobhan Hughes contributed to this article.

Write to Jared Favole at jared.favole@dowjones.com and Stephen Power at stephen.power@wsj.com

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