The U.S. could send military planners to help West Africa's regional bloc quell an Islamist and ethnic insurrection in the north of Mali, U.S. Assistant Secretary of State for African Affairs Johnnie Carson said Wednesday.

But confusion over the bloc's strategy is stalling the U.S. from lending such support as a civil war in the continent's third-biggest gold producer continues into a fifth month, Carson told reporters on a conference call.

Mali, a West African nation the size of California and Texas combined, has been upended since early January when rebels, many trained by the regime of late Libyan leader Col. Moammar Gadhafi, embarked on a push to liberate a stretch of the country's north.

The Economic Community of West African States, or Ecowas, an alliance of 15 West African nations, has put as many as 3,000 soldiers on standby for deployment to the region. There they would face two entrenched and broadly-aligned rebel armies--one an Islamist militia seeking to impose fundamentalist law; the other a separatist insurgency looking to create an ethnic homeland state for the Sahara's Tuareg people.

"We have been willing to provide logisticians and planners" to that operation, Carson said. "But the mission and role must be defined before we make any kind of commitment."

Mali's civil war--and the accompanying mass exodus of more than 200,000 civilians--has so far carried limited direct impact on the roughly 50 metric tons of gold the country produces yearly. Most of Mali's mining occurs in its peaceful south.

A bigger threat to production has been the regional response to a March 22 coup, which saw junior officers end a 20-year stretch of democracy in a part of the Sahara where elections are rare.

In the wake of the coup, regional neighbors briefly enforced border closures and financial sanctions meant to pry the military from power. That forced the junta to allow a transitional government to form, yet they still effectively hold final say in the country's plans to hold eventual elections, analysts say.

Monday, Ecowas warned it could reinstate sanctions if coup leaders don't completely relinquish power.

"The U.S. fully supports Ecowas's mediation efforts to help Mali return to democratic rule," Carson said. "The military must step aside completely. Those who have illegally seized power have no right to remain in power and no strength to address the serious security and humanitarian issues that Mali faces today."

In Nigeria, which is also fighting an Islamist insurrection in its desert like north, the U.S. is training military, police, and secret service personnel to better analyze bomb blasts, gather forensic evidence and conduct interrogations, Carson said.

Africa's most populous nation is grappling to quell the Boko Haram militia, which has killed more than 1,000 people in that past two years.

-By Drew Hinshaw, Dow Jones Newswires; +221 77 698 45 61; drew.hinshaw@dowjones.com