(CNN)President Obama will continue his Gulf Coast visit Tuesday with a stop in Florida’s Panhandle, where beaches have started to see signs of oil as crude continues to gush from a ruptured deepwater well.

Obama, on his fourth trip to the region since oil began spewing from the well in April, is scheduled to return to Washington later Tuesday and address the nation about the situation from the Oval Office.

But first, Obama will give a speech of support for oil-impacted communities and American troops while at Pensacola’s Naval Air Station Tuesday morning, an administration official said.

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Meanwhile Rep. Ed Markey, D-Massachusetts, will have a chance to grill executives from five major oil companies on Capitol Hill.

The witness list for Tuesday’s hearing of his House Energy and Environment subcommittee includes chief executives of BP, ExxonMobil, Chevron, ConocoPhillips and Shell Oil.

Markey, a longtime opponent of offshore drilling and vocal critic of BP’s response to the oil disaster, said that the purpose of the hearing is to “establish whether or not BP is the rule or the exception” in terms of its ability to respond to a massive oil spill.

As efforts continued to clean up the oil, BP turned to a new source for help on Monday: actor Kevin Costner.

The company ordered 32 machines designed by Costner, who said they separate oil from water and recycle the crude at the same time.

“This is the key, it’s the linchpin to people going back to work. It’s certainly a way to fight oil spills in the 21st century,” Costner said in an exclusive interview on CNN’s AC360.

Louisiana residents will have a chance to talk to experts about their efforts to deal with oil spill damage Tuesday during an open house hosted by the Coast Guard, wildlife, environmental and BP officials.

Obama spent much of Monday touring Mississippi and Alabama. On Monday Obama assured Gulf Coast residents that the “full resources of the federal government are being mobilized to confront” the disaster that has emptied beaches, docked fishing boats and ruined precious marshlands.

Political pressure on BP is mounting.

Senate Majority Leader Harry Reid of Nevada, along with most other Senate Democrats, sent a letter to embattled BP chief Tony Hayward on Monday, urging the company to set aside $20 billion for the purposes of covering both economic damages and Gulf cleanup costs.

A letter released Monday to Hayward from House Energy and Commerce Committee Chairman Henry Waxman, D-California, stated that a congressional investigation indicates the company took a low-cost, speedy approach to drilling the now-broken deepwater well responsible for the growing spill in the Gulf of Mexico.

“(Our) investigation is raising serious questions about the decisions made by BP in the days and hours before the explosion” that created the spill, Waxman noted. “On April 15, five days before the explosion, BP’s drilling engineer called (the facility in the Gulf) a ‘nightmare well.'”

Hayward is scheduled to testify before Waxman’s committee on Thursday.

On Wednesday Obama and top BP officials have a highly anticipated meeting, where they are expected to discuss a new structure for processing damage claims from the disaster.

David Axelrod, Obama’s senior adviser, has said a new claims plan would call for an independent third party to handle the process, and a White House spokesman said Monday that the administration is confident that it has the legal authority to force BP to set up an escrow account for the purpose of paying damages.

Obama said Monday that preliminary talks on the restructuring had already begun, but he was cautious about how much progress could be made before Wednesday’s meeting and declined to elaborate on any possible agreement.

Oil is believed to have been pouring into the Gulf since the April 20 explosion that sank the offshore drill rig Deepwater Horizon, killing 11 workers. The spill now dwarfs the 11 million gallons that were dumped into Alaska’s Prince William Sound when the tanker Exxon Valdez ran aground in 1989, and oil in varying amounts and consistencies has hit the shores of Louisiana, Mississippi, Alabama and Florida.

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