Talks between Nigeria's leading petroleum workers' union and officials with ExxonMobil failed Wednesday to produce a solution that would end the seven-day strike that is reportedly costing the American energy firm some 800,000 barrels of production per day.

While earlier reports in the Nigerian media said the country's largest oil union, PENGASSAN, agreed to return to work during the course of talks, leaders for the workers denied it, keeping the taps at ExxonMobil in Nigeria shut for another day.

Earlier this week, a representative for the Nigerian National Petroleum Corp. -- mediators of the talks -- said Nigerian workers were calling for a 25 percent increase in pay, improved working conditions and a better pension plan.

In observance of the May 1 workers' day holiday, both sides said the talks would not reconvene until Friday.

PENGASSAN's grievance with ExxonMobil began last month when the union threatened to walk off the job in protest of the company's decision to fire 100 union workers.

ExxonMobil officials have since denied any wrongdoing, saying those employees were given generous compensation packages during the current round of restructuring.

Grievances with oil companies operating in the petroleum-rich Niger Delta are not uncommon, said Rolake Akinola, a senior analyst for West Africa at the London-based consulting firm Control Risks.

"These kind of strike threats are a sort of trend (in the Niger Delta)," Akinola told United Press International. "That's the cycle we've seen in the oil industry."

And while some consider an impending strike a harbinger of even more difficult times, Akinola disagrees, saying there is sufficient nonunion labor to keep production online, at least for the short term.

She noted that since 1999 the handful of strikes by oil workers in the delta did not diminish production by more than 5 percent for the durations of the walkouts. Akinola said the production shortfalls caused by a potential strike remained insignificant compared with the ongoing violence attributed to gangs and militant groups in the delta.

Producing just over 2 million barrels a day, Nigeria's oil sector is experiencing a 20 percent shortfall from just a few years prior, before widespread militants began stepping up attacks on foreign oil installations and kidnapping workers.

Militants contend that the Nigerian government, along with the foreign oil companies operating in the delta, have benefited enormously over the years from the sale of the nation's oil and gas reserves, though they have done little to help the residents of the region who live in poverty.

Since the 1970s, Nigeria, Africa's No. 1 oil producer, has pumped more than $300 billion worth of crude from the southern delta states, according to estimates. But high unemployment in the delta, environmental degradation due to oil and gas extraction, and a lack of basic resources such as fresh water and electricity have angered some of the region's youth and incited them to take up arms.

ExxonMobil is not the only foreign firm in Nigeria to experience labor difficulties.

In March, the International Federation of Chemical, Energy, Mine and General Workers' Unions accused oil giant Mobil Oil Nigeria Plc. of unfair business practices and ill-treatment of local union laborers.

According to Nigerian labor officials, Mobil in Nigeria fired those union leaders seeking a collective-bargaining agreement for their workers.

"Mobil Oil Nigeria has betrayed our trust," said PENGASSAN General Secretary Bayo Olowoshile at the time.

"These recent actions are premeditated attempts to victimize and harass union officers, frustrate legal justice, and they amount to a serious breach of our existing labor agreement, national industrial law, and global labor standards."