COVINGTON, Louisiana (AP) — The Obama administration’s environmental chief dipped a small cup into the oily mess at the mouth of the Mississippi and was surprised by what came out.

“Oh my God — it’s so thick!” exclaimed Environmental Protection Agency Administrator Lisa Jackson who toured delicate coastal wetlands that have been invaded by the black and orange crude.

She was one of several top administration officials in the Gulf Coast this week as the White House is facing increasing questions about why the government can’t assert more control over the handling a massive oil spill in the Gulf of Mexico, which unfolded after a BP offshore drilling rig blew up April 20.

The administration’s point man on the spill rejected the notion of removing BP and taking over the crisis Monday, saying the government has neither the company’s expertise nor its deep-sea equipment.

“To push BP out of the way would raise a question, to replace them with what?” Coast Guard Commandant Thad Allen, who is heading the federal response to the spill, said at a White House briefing.

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A memorial service was scheduled for Tuesday afternoon in Jackson, Mississippi, for the 11 workers who were killed when the oil rig exploded. The event was being held by Transocean, which owned the rig.

All of BP’s attempts to stop the leak have failed, despite the oil giant’s use of joystick-operated submarine robots that can operate at depths no human could withstand. Millions of gallons of brown crude are now coating birds and other wildlife and fouling the Louisiana marshes.

Those that Jackson surveyed by boat have been battered for centuries by hurricanes and man-made canals that led to drastic erosion.

A crew used a machine to separate oil from water and slowly filled a four-foot (1.2-meter) high storage tank with crude. For oil deeper in the marsh, little could be done and the vegetation there was expected to die.

“At a minimum what we can say is dispersants didn’t work here,” Jackson said. “When you see stuff like this, it’s clear it isn’t a panacea.”

Jackson said she worried further erosion from oil-damaged marshes would leave her nearby hometown of New Orleans even more exposed to future storms.

BP is pinning its hopes of stopping the gusher on yet another technique never tested 5,000 feet (1,524 meters) underwater: a “top kill,” in which heavy mud and cement would be shot into the blown-out well to plug it up. The process could begin as early as Wednesday, with BP CEO Tony Hayward giving it a 60 percent to 70 percent chance of success.

Allen said federal law dictated that BP had to operate the cleanup, with the government overseeing its efforts.

“They’re exhausting every technical means possible to deal with that leak,” he said. “I am satisfied with the coordination that’s going on.”

Interior Secretary Ken Salazar suggested over the weekend that the government could intervene aggressively if BP wasn’t delivering. “If we find that they’re not doing what they’re supposed to be doing, we’ll push them out of the way appropriately,” he said.

But asked about that comment Monday, Allen said: “That’s more of a metaphor.”

Allen said BP and the government are working together, with the government holding veto power and adopting an “inquisitorial” stand toward the company’s ideas.

BP said it is doing all it can to stop the leak. Its chief operating officer, Doug Suttles, made the rounds of network morning news shows to say that the company understands people are frustrated.

“Clearly Secretary Salazar is telling us that we need to do this as expediently as we can,” Suttles said. “And of course we are.”

Hayward, BP’s chief executive, walked along oil-soaked Fourchon Beach and said he had underestimated the possible environmental effects.

“I’m as devastated as you are by what I’ve seen here today,” Hayward told reporters after he spoke with cleanup workers in white overalls and yellow boots, some shoveling oily sand into garbage cans. “We are going to do everything in our power to prevent any more oil from coming ashore, and we will clean every last drop up and we will remediate all of the environmental damage.”

Engineers are working on several other backup plans in case the top kill doesn’t work, including injecting assorted junk into the well to clog it up, and lowering a new blowout preventer on top of the one that failed.

The only certain permanent solution is a pair of relief wells crews have already started drilling, but the task could take at least two months.

In another source of tension between BP and the government, the company was still using a certain chemical dispersant Monday to fight the oil despite orders from the Environmental Protection Agency to employ something less toxic.

“If we can find an alternative that is less toxic and available, we will switch to that product,” said Suttles.

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Associated Press Writers Erica Werner and Matthew Daly in Washington and Kevin McGill and Alan Sayre in Louisiana contributed to this report.

Copyright 2010 The Associated Press.