Mauritania reacted furiously on Monday after the United States pulled its status as a preferential trade partner, accusing the West African state of tolerating forced labour and hereditary slavery.The decision, made by Washington last Friday, will terminate Mauritania's eligibility for trade preference starting January 1.Mauritanian government spokesperson Mohamed Ould Maham lashed the move on Monday on Twitter, calling it "a betrayal of the friendly relations between our countries and a denial of our efforts" to roll back slavery practices.He pointed to President Donald Trump's posture towards Saudi Arabia, implying that Riyadh - under fire over the murder of dissident journalist Jamal Khashoggi - got soft treatment because of its purchases of US weapons."Would Trump have taken this decision if he was expecting a $110bn arms contract with us?" he asked rhetorically.The United States said the decision was based on an annual review of eligibility under the African Growth and Opportunity Act, which requires African countries to improve rule of law and uphold respect for human rights and labour standards."Mauritania has made insufficient progress toward combating forced labour, in particular the scourge of hereditary slavery," the US Trade Representative said in a statement."In addition, the government of Mauritania continues to restrict the ability of civil society to work freely to address anti-slavery issues."Remnants of traditional slavery have become a major issue in Mauritania, an impoverished, deeply conservative and predominantly Muslim state. Under a generations-old system of servitude, members of a "slave" caste are forced to work without pay, typically as cattle herders and domestic servants.Slavery was officially abolished in 1981. In 2015, parliament made slavery "a crime against humanity" punishable by prison terms of up to 20 years, compared with five to 10 years previously. No official figures exist for those still enslaved, but some NGOs estimate that up to 43 000 people remained in bondage in 2016, accounting for around one percent of the population. Hundreds of thousands of Mauritanians are the descendants of slaves.Activists say the country has made little headway towards eradicating the problem, although specialised courts set up in 2015 have notably come down harder on offenders this year.In March, a court in the Atlantic port of Nouadhibou sentenced a father and his son to 20 years in prison for enslaving a family of four. A woman was jailed for 10 years for doing the same to three sisters.In April, the court in the coastal capital Nouakchott gave three men the maximum sentence of a year behind bars for denigrating others by addressing them like slaves, a first for such a crime.Despite the symbolic power of the US decision, bilateral trade is negligible.According to official Mauritanian figures, Mauritania imported US goods worth $91.4m in 2017, and exported just $1.5m.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.