U.S. Transportation Secretary Rodney E. Slater, leading a trade mission in support of President Clinton's commitment to a well-integrated Western Hemisphere transportation system, joined with Brazilian Transport Minister Eliseu Lemos Padilha in signing a major three-year maritime agreement ensuring each country's shipping lines will be treated equally when carrying cargo from the other country. "On behalf of President Clinton and Vice-President Gore, we are pleased we've reached an agreement that promotes the principle of reciprocity in the shipping relations between the U.S. and Brazil," Secretary Slater said. The agreement ensures each country's national-flag shipping lines equal access to commercial cargoes and to cargoes whose shipment is controlled by the other country's government…