Angry Louisians watched fragile shorelines and rare birds become coated in thick crude Monday as BP came under mounting pressure ahead of a make-or-break "top kill" operation to stem the tide of oil streaming into the Gulf of Mexico.

Meanwhile, The New York Times reports that "state and federal officials feuded with BP over its failure to meet deadlines and its refusal to stop spraying a toxic dispersant."

The oil company had indicated that it could stem the flow of oil on Tuesday by trying a procedure known as a top kill, in which heavy fluid would be pumped into the well. But on Monday morning the company’s chief operating officer said the procedure would be delayed until Wednesday. At the same time, BP was locked in a tense standoff with the Environmental Protection Agency, which had ordered the company to stop using a toxic chemical dispersant called Corexit by Sunday.

But BP continued spraying the chemical on Monday, despite the E.P.A.’s demand that it use a less toxic dispersant to break up the oil. The company told the agency that no better alternative was available.

With pictures of oiled pelicans and ruined marshland dominating the newspapers, BP hit back with a PR offensive, taking out ads in The New York Times and The Wall Street Journal and pledging up to 500 million dollars to study the impact of the spill.

BP chief operating officer Doug Suttles said the delayed "top kill" operation to inject heavy drilling fluid into the leak and then hopefully seal the well with cement would now begin first thing on Wednesday morning.

Asked in a CNN interview what the chance of success was for an operation that will be performed by remote-controlled submarines 5,000 feet (1,500 meters) down on the seabed, Suttles gave it a six or a seven out of 10.

"We are going to give it every shot. We are going to make sure everything is ready before we go. We need it to work."

Louisiana Governor Bobby Jindal and top US federal officials have expressed doubts in BP's ability to stop the leak and have warned they may be pushed out of the way if progress is not made soon.

"We met today to take action, take matters into our own hands," a frustrated Jindal told reporters Sunday in the port of Venice, which represents the frontline in the battle to stave off a looming environmental catastrophe.

Local residents were taking out their own boats and commandeering idle Coast Guard vessels to lay protective booms around a bird sanctuary, where several birds have already been coated in oil and taken it back to their nests.

The BP-leased Deepwater Horizon rig exploded on April 20, killing 11 workers, and sank two days later. Ever since, hundreds of thousands of gallons of oil, perhaps even millions, have been spewing each day into the sea.

President Barack Obama's administration, under pressure itself for its response to the crisis, is insisting the full force of the federal government is bearing down on BP.

"If we find that they're not doing what they're supposed to be doing, we'll push them out of the way," Interior Secretary Ken Salazar said Sunday, lashing out at BP for missing "deadline after deadline" to cap the leak.

"Do I have confidence that they know exactly what they're doing? No, not completely," he added, saying the company faced an "existential crisis."

But Suttles, adamant that BP was doing everything in its power, pointed out that really the US authorities have little choice as the British energy giant alone has the necessary expertise to end this disaster.

"I don't think anyone else could do better than we are," Suttles told CNN. "I know that's frustrating to hear and our performance to this point I wish was better. I wish this was done. We are doing everything we can."

If the "top kill" fails, relief wells to divert the flow and allow the leaking well to be sealed won't be ready till August at the earliest, meaning tens of millions of barrels of crude could stream into the Gulf of Mexico.

According to the most conservative estimates, more than 6.5 million gallons of crude has already spilled into the sea from the riser pipe that once connected the Deepwater Horizon to the wellhead a mile below.

But analysis by independent scientists suggests the actually many times bigger, possibly too much already for the region's fragile ecology -- and local communities so reliant on fishing and tourism -- to bear.

The amount of oil being suctioned up by a mile-long insertion tube slowed Sunday to 1,360 barrels a day from the previous average of about 2,100, only a fraction of the total gusher.

The cost of the clean-up also continued to mount. BP said in London Monday that the operation had so far cost the company 760 million dollars (607 million euros).

A sign of how much BP figures this disaster will eventually cost it was evident in the fact it was willing to pledge Monday half-a-billion dollars for a 10-year research program to study the impact of the spill on the environment.

It has also started advertising in major US newspapers to try to reassure skeptical Americans that it can be trusted to stop and clean up the spill.

"Since the tragic accident on the Transocean Deepwater Horizon rig first occurred, we have been committed to doing everything possible to stop the flow of oil at the seabed and keep it away from the shore," the ad says.

(with AFP report)