A sharp increase in pirate attacks in the Atlantic Ocean off West Africa is threatening plans to double oil production from 4 million barrels a day amid a swelling energy boom in the largely impoverished region.

U.S. company Anadarko Petroleum Corp. and oil companies have reported new discoveries off Liberia and Sierra Leone in recent weeks, heightening expectations that the war-scarred region is heading for a major bonanza.

Given the region's location on the Atlantic, allowing direct supplies to the United States without the dangers plaguing Middle Eastern exports, the region is expected to provide the United States with about one-quarter of its crude imports by 2015.

Most of the attacks involve theft, particularly large amounts of oil, rather than hijackings for ransom, the primary tactic used by the Somali pirates.

"Gulf of Guinea attacks have been … targeted almost solely against oil- and diesel-carrying vessels," Oxford Analytica noted in a recent report.

So any serious threat to supplies could have an impact in the United States.

On top of all this, there's the problem of increased cocaine smuggling from Latin America to Europe through Guinea-Bissau and other struggling West African states, plus widespread political upheaval in Nigeria, a key African producer and supplier to the United States, involving Muslim militants.

The piracy problem centers on the Gulf of Guinea, one of the main offshore oil zones and which stretches along the coasts of a dozen countries from Guinea southward to Angola, another major African oil producer.

The scale of the problem hasn't reached the proportions of the crisis in East Africa, where highly organized and increasingly sophisticated Somalia pirate gangs prey on oil tankers and other shipping in the Gulf of Aden and deep into the Indian Ocean.

But attacks of West Africa are steadily mounting and becoming more violent, U.N. Undersecretary-General B. Lynn Pascoe warned the U.N. Security Council Feb. 28.

Pascoe cited 64 attacks in 2011 off nine countries, including Benin, the Ivory Coast, Congo-Brazzaville, Ghana and Nigeria. That compares to 45 attacks off seven countries in 2010.

In Nigeria, a long-simmering insurgency in the oil-rich Niger Delta appears to be igniting again, with oil theft a major industry.

The Nigerian violence slashed oil production by 40 percent to around 2 million barrels per day before a government amnesty halted fighting in the delta in 2009.

The United Nations' International Maritime Organization said it has recorded 10 attacks off West Africa in January-February. Pasco stressed, "We know that not all piracy incidents are systematically reported."

Some shipowners are reluctant to report incidents to avoid having insurance premiums hiked, particularly if illegal cargoes are involved.

"In Nigeria, it's estimated that approximately 60 percent of pirate attacks go unreported," London security firm AKE Ltd says.

The Security Council urged the regional states to develop "a united front to respond effectively to the growing threat of piracy along their coasts."

The prospects of that are slim. With the exception of Nigeria, none of these states, where corruption is rife and security forces weak, under-manned and under-equipped, have the infrastructure or the funds to be able to effectively take on the pirates.

"Nigerian counter-piracy efforts have been beginning to register success but one result has been to push gangs' activities further along the West African coast -- and further out to sea," Oxford Analytica observed.

This is what happened off Somalia. International naval forces deployed to counter the pirates there only resulted in the marauders employing larger deep-water vessels that allow them to operate up to 1,500 nautical miles eastward into the Indian Ocean and in the tanker lanes off the Persian Gulf.

No statistics regarding the cost of West African piracy have been released. But the Somali pirates' depredations cost the international community up to $9 billion a year, said Geopolicity Inc., a consultancy that specializes in Middle Eastern and Asian economic intelligence.

That could escalate to $13 billion-$15 billion by 2015.

Lloyd's Market Association, a London umbrella for a group of insurers, listed Nigeria, Benin and nearby waters in the same risk category as lawless Somalia. That could signal higher insurance rates for shipping, including oil traffic, off West Africa.