Biram Ould Dah made a trip to neighboring Mali on Thursday in a bid to draw support from human rights activists there.
Though outlawed, slavery still exists in the West African nation ofMauritania. Last month, some 13 members of an organization fighting to end it were sentenced to prison time ranging from three to 15 years.
The activist says the Mauritanian group plans to bring up the sentences at an African Union meeting in Gambia in October.
Mauritania's government has accused the activists of using violence to pursue their cause, a charge the group denies.