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With the European Union agreeing to join a U.S.-led boycott of crude produced by Iran, analysts point to the opportunity, as well as the possible need, for others to increase production.

The fifth-largest oil provider for the U.S., Nigeria delivered about 850,000 barrels a day last year. It supplies U.S. refineries with about 9 percent of their daily crude intake.

The country’s potential to play a bigger role in global oil markets likely bolsters U.S. eagerness to help Mr. Jonathan prevent a security meltdown.

Nigeria is the African country of greatest strategic importance to the United States, and therefore we have to be concerned about the stability of its government,” said John Campbell, a senior fellow at the Council on Foreign Relations who served as U.S. ambassador to Nigeria from 2004 to 2007.

While “stability is being challenged right now by Boko Haram,” Mr. Campbell said, the threat can be overcome and could carry on in its current form for “quite some time” before Nigeria’s oil industry is at risk.

He added that the Boko Haram threat differs significantly from what disrupted Nigerian oil output four years ago, when militants from the mainly Christian southern delta forced the shutdown of an offshore Shell platform with a brazen, nighttime speedboat raid.

Such disruptions ended in 2009, when President Umaru Musa Yar’Adua, a Muslim, cut a deal with the southern militants that involved significant payoffs and amnesty.

The southern militants have not presented problems for Mr. Jonathan, but they have threatened to resume attacks on the oil industry should the government try to cut a similar amnesty deal with northern groups such as Boko Haram.

Mr. Jonathan signaled a desire to negotiate with Boko Haram last week, calling on the group publicly to identify itself and state its demands.

While such developments are playing out, some analysts say the greatest threat to Nigeria’s oil industry is posed not by militant groups but searing public frustration over poverty and the government.

“The main challenge to Nigeria’s oil exports would be in the event of a confrontation between the government and the public over the lifting of the fuel subsidy, particularly if that provoked the oil unions to strike,” said Peter Lewis at Johns Hopkins University’s School of Advanced International Studies.

“If the powerful unions in the petroleum sector go on strike, they could shut down the oil supplies,” Mr. Lewis said.

“Even then, it’s likely that it would be short action, but the oil futures markets would register, and it would probably dramatically boost prices.”