President Barack Obama, whose approval ratings have been hurt by his administration's perceived slow response to the spill, welcomed the latest developments.
"The long battle to stop the leak and contain the oil is finally close to coming to an end," he said.
BP's mile-deep Macondo well ruptured after an oil rig exploded and sank on April 20, spewing up to 5 million of barrels of oil into the ocean for nearly three months in the world's worst accidental marine spill.
After months of setbacks in efforts to permanently plug the well, BP said heavy drilling mud injected into it on Tuesday was stemming the flow of crude. The next step in the "static kill" procedure will be to pump in cement behind the mud as a seal.
The static kill is part of a two-pronged strategy to kill the well for good. A relief well is due to intercept the ruptured well shaft in mid-August so that more mud and cement can be injected into it.
Welcoming the government report titled "What Happened to the Oil?” Carol Browner, Obama's energy adviser, told ABC's "Good Morning America" show, "We do feel like this is an important turning point."
US scientists said in the report that burning, skimming and direct recovery had removed one quarter of the oil, another 25 percent had naturally evaporated or dissolved, and 24 percent had been dispersed, either naturally or chemically.
The rest was either on or just beneath the water's surface as "light sheen or weathered tarballs," had washed ashore or was buried in sand and sediments at the sea bottom, they said.
However, more than 1 million barrels of oil remains in the Gulf, four times the estimated 257,000 barrels that spilled into Prince William Sound from the Exxon Valdez tanker in 1989.
The financial implications for BP's continued cleanup efforts were not immediately clear. Government officials have said in the past that it will take years to fully repair the damage inflicted by the spilled oil, which seeped into sensitive wetlands and marshes and soiled miles/kilometers of coastline.
The spill also disrupted the livelihoods of fishermen and tourism operators and triggered a barrage of damages lawsuits against BP, which has said it will pay all legitimate claims.
Earlier this week, government scientists reported that up to 5 million barrels of oil may have leaked from the BP well before it was temporarily capped on July 15.
That could spell bad news for BP, which had estimated the well had leaked 4 million barrels of oil and that it would be fined $1,100 per barrel under the Clean Water Act. It faces fines of $4,300 per barrel if gross negligence is proven.
BP stock rose 1.44 percent in London, while US-listed shares trading in New York rose briefly before sliding down about 1 percent. BP stock has recovered about half way from its low point in late June but remains well below its April pre-spill high.
"They're at a critical point here as far as stopping the leak, maybe with the good news on the horizon a lot of investors have bought the stock" said Alan Lancz, president of Alan B. Lancz & Associates Inc., an investment advisory firm in Toledo, Ohio.
BP has suspended dividend payments, ringfenced $20 billion, and put billions of dollars of its assets up for sale to help pay for its liabilities.
Anadarko Petroleum Corp, one of BP's partners in the well, said on Tuesday it had secured $6.5 billion in loan commitments, in part to pay for its liabilities.
