In a statement, Obama said the three countries had failed to make continual progress in meeting the U.S. requirements for the African Growth and Opportunity Act.

"Each of these countries has experienced an undemocratic transfer of power, which is incompatible with making progress toward establishing the rule of law or political pluralism," the statement said, according to Reuters.

"These circumstances also make it extremely difficult to achieve the progress necessary to satisfy the other AGOA eligibility criteria," the statement added.

However, Obama said he was adding Mauritania, earlier suspended for a 2008 military coup, to the list of sub-Saharan African countries eligible for preferential U.S. tariff treatment under the program, according to a White House official quoted by Reuters.

The United States offers duty-free treatment for nearly 6,400 eligible items such as clothing, cocoa, wood, leather, processed foods and cut flowers under the African Growth and Opportunity Act.

To be eligible for the AGOA, a country must make continual progress to establish the rule of law and political pluralism. Also, the protection of human rights, workers rights and efforts to fight corruption must be in place.

The United States imported $324.3 million worth of goods from Madagascar, $106.4 million from Guinea and $44.3 million from Niger in 2008, according to Reuters.