Officials at the Environmental Protection Agency are considering whether to bar BP from receiving government contracts, a move that would ultimately cost the company billions in revenue and could end its drilling in federally controlled oil fields.

Over the past 10 years, BP has paid tens of millions of dollars in fines and been implicated in four separate instances of criminal misconduct that could have prompted this far more serious action. Until now, the company's executives and their lawyers have fended off such a penalty by promising that BP would change its ways.

That strategy may no longer work.

Days ago, in an unannounced move, the EPA suspended negotiations with the petroleum giant over whether it would be barred from federal contracts because of the environmental crimes it committed before the spill in the Gulf of Mexico. Officials said they are putting the talks on hold until they learn more about the British company's responsibility for the plume of oil that is spreading across the Gulf.

The EPA said in a statement that, according to its regulations, it can consider banning BP from future contracts after weighing "the frequency and pattern of the incidents, corporate attitude both before and after the incidents, changes in policies, procedures, and practices."

Several former senior EPA debarment attorneys and people close to the BP investigation told ProPublica that means the agency will re-evaluate BP and examine whether the latest incident in the Gulf is evidence of an institutional problem inside BP, a precursor to the action called debarment.

Federal law allows agencies to suspend or bar from government contracts companies that engage in fraudulent, reckless or criminal conduct. The sanctions can be applied to a single facility or an entire corporation. Government agencies have the power to forbid a company to collect any benefit from the federal government in the forms of contracts, land leases, drilling rights, or loans.

The most serious, sweeping kind of suspension is called "discretionary debarment" and it is applied to an entire company. If this were imposed on BP, it would cancel not only the company's contracts to sell fuel to the military but prohibit BP from leasing or renewing drilling leases on federal land. In the worst cast, it could also lead to the cancellation of BP's existing federal leases, worth billions of dollars.

Present and former officials said the crucial question in deciding whether to impose such a sanction is assessing the offending company's culture and approach: Do its executives display an attitude of non-compliance? The law is not intended to punish actions by rogue employees and is focused on making contractor relationships work to the benefit of the government. In its negotiations with EPA officials before the Gulf spill, BP had been insisting that it had made far-reaching changes in its approach to safety and maintenance, and that environmental officials could trust its promises that it would commit no further violations of the law.

EPA officials declined to speculate on the likelihood that BP will ultimately be suspended or barred from government contracts. Such a step will be weighed against the effect on BP's thousands of employees and on the government's costs of replacing it as a contractor.

Even a temporary expulsion from the U.S. could be devastating for BP's business. BP is the largest oil and gas producer in the Gulf of Mexico and operates some 22,000 oil and gas wells across United States, many of them on federal lands or waters. According to the company, those wells produce 39 percent of the company's global revenue from oil and gas production each year -- $16 billion.

Discretionary debarment is a step that government investigators have long sought to avoid, and which many experts had considered highly unlikely because BP is a major supplier of fuel to the U.S. military. The company could petition U.S. courts for an exception, arguing that ending that contract is a national security risk. That segment of BP's business alone was worth roughly $4.6 billion over the last decade, according to the government contracts website USAspending.