President Barack Obama on Tuesday revoked South Sudan’s eligibility for the US preferential trade programme, the Africa Growth and Opportunity Act (Agoa). Obama also removed Gambia from the programme and reinstated Guinea-Bissau. All these moves take effect on January 1.

A presidential proclamation announcing the actions did not specify the reasons for declaring South Sudan and Gambia ineligible for Agoa benefits. It instead referred to general standards for eligibility included in the law that established Agoa in 2000.

Two of the requirements are that a country “does not engage in activities that undermine the US national security or foreign policy interests” and “does not engage in gross violations of internationally recognised human rights.”

The US has previously slapped sanctions on four South Sudan military leaders for their roles in the year-long civil war that has resulted in tens of thousands of civilian deaths.

Washington is also drafting a resolution in the United Nations Security Council that would impose international sanctions on South Sudanese found to be impeding settlement of the conflict.

President Obama’s action on Gambia appears to be a response to alleged human- rights abuses by the West African country’s government, including the recent enactment of a law under which persons convicted of “aggravated homosexuality” face life imprisonment.

Expulsion from Agoa has largely symbolic significance in both cases. Neither South Sudan nor Gambia benefits appreciably from the programme, which permits unlimited quantities of goods from eligible countries to enter the US duty-free.

Gambia’s exports to the US last year were valued at $2 million, while South Sudan sold $29,000 worth of forest products to US buyers last year.

A total of 40 sub-Saharan nations will be eligible to participate in Agoa in 2015.