EXCLUSIVE - Fight between U.S. and Brazil threatens trade

WASHINGTON/BRASILIA (Reuters) - The road to rock bottom for relations between Brazil and the United States, a dispute that now threatens business ties between the two Western Hemisphere economic giants, began in Brasilia in March.

U.S. Secretary of State Hillary Clinton was trying to convince Brazilian President Luiz Inacio Lula da Silva to drop or postpone his controversial efforts to negotiate a nuclear deal with Iran, and support a new round of sanctions instead.