Niger's President Mamadou Tandja (file photo)

Political opponents of Niger's President Mamadou Tandja say they are determined to block a referendum to extend his rule. The White House says it is concerned about President Tandja ruling by decree after dissolving a constitutional court that said his planned referendum is illegal.

Though Wednesday's call for a nationwide strike met with only limited success, Niger President Mamadou Tandja's political opponents say they will continue to demonstrate against his plans to stay in power.

Ala Mogaskiya from Niger's opposition Front for the Defense of Democracy says President Tandja's move to rule by decree is an attempt to subvert civilian democratic rule.

The Front for the Defense of Democracy is calling for soldiers to ignore the president's orders, but a statement from Niger's military says it will remain neutral in the dispute.

White House spokesman Robert Gibbs says President Tandja's actions undermine efforts during the past 10 years to advance good governance and the rule of law in Niger.

In a written statement, Gibbs says the United States is concerned about President Tandja ruling by decree and dissolving the national assembly and the constitutional court as part of a bid to retain power beyond his constitutionally limited mandate.

The European Union says President Tandja's efforts to stay in power could threaten financial aid to one of the world's poorest countries.  France says Mr. Tandja's actions are unconstitutional.

The Economic Community of West African States says it may impose sanctions on Niger.  The organization of French-speaking countries is urging the government to observe the rule of law, saying developments in Niger will be addressed at next Friday's meting of the Permanent Council of the Francophony.

But President Tandja appears determined to press ahead with a referendum August 4 to allow him a third term once his second term expires in December.  Niger's 1999 constitution prohibits any amendment regarding the president's term of office.

While many shops in the capital ignored Wednesday's call for a nationwide strike, local radio stations report there was greater support in other areas, including the city of Zinder.