In April 2013, the United States proposed that MINURSO monitored human rights (as all the other UN mission since 1991) in Western Sahara, a move that Morocco strongly opposed, cancelling the annual African Lion military exercises with U.S. Army troops. Also in mid-April, United States Ambassador to Morocco Samuel L. Kaplan declared during a conference in Casablanca that the Moroccan autonomy plan "can't be the only basis in these negotiations", referring to the UN sponsored talks between the Polisario Front and Morocco.