 Complete the following phrase:  In the late 1970s, Cubas relations with North American states improved during the period with Mexican President Luis Echeverría, Canadian Prime Minister Pierre Trudeau, and U.S. President Jimmy Carter in power. Carter continued criticizing Cubas human rights abuses, but adopted a respectful approach which gained Castros attention. Considering Carter well-meaning and sincere, Castro freed certain political prisoners and allowed some Cuban exiles to visit relatives on the island, hoping that in turn Carter would abolish the economic embargo and stop CIA support for militant dissidents. Conversely, his relationship with China declined, as he accused Deng Xiaopings Chinese government of betraying their revolutionary principles by initiating trade links with the U.S. and 