The Organization of American States has suspended Honduras over the ousting of President Manuel Zelaya a week ago.
The rare decision was made at an emergency meeting of the 35-member organisation in Washington.
Manuel Zelaya, who took power in 2006 and was due to leave office in 2010, was bundled into exile by the military last Sunday after a dispute over presidential term limits.
The coup has been widely condemned abroad.
There are fears of a violent showdown as crowds gather in the capital Tegucigalpa ahead of Mr Zelaya's expected return to Honduras on Sunday.
Mr Zelaya confirmed to a television news station in Venezuela that he will return to his country on Sunday, and do so with "several presidents" of allied countries.
Shortly beforehand, Catholic leaders warned that a return by Mr Zelaya to the country "could provoke a bloodbath."
Thousands of Mr Zelaya's supporters and opponents have demonstrated daily since the president was exiled to Costa Rica, and brief clashes have broken out between the army and protesters.
Ecuadoran President Rafael Correa reiterated he was ready to go to Honduras on Sunday with Mr Zelaya, along with the presidents of Argentina and Paraguay.
Mr Zelaya was ousted by troops and exiled to Costa Rica on 28 June, because of what his critics say was an illegal attempt to lift the limit on the presidential term.