In the article, constructions with the conjunctions or, either ... or, if ... or, whether ... or, containing antonyms, synonyms and words of different semantic groups, are investigated in the official speeches of the US presidents George Bush Sr., Bill Clinton, George Bush Jr., Barack Obama, Donald Trump. The methods of contextual and discourse analysis help to reveal the universal features and individual peculiarities in the functioning of these syntactic structures in the American presidential discourse. The above-mentioned conjunctions join regular lexical and syntactic antonyms existing in the language system, as well as contextually determined antonyms which can even belong to different levels of the language and various parts of speech. Constructions of this type are used in resolute and uncompromising statements of the American presidents in order to underline the supremacy and strength of their country, stir up the feeling of integrity and patriotism in the audience, and persuade people to follow the ideas of freedom and democracy and support the tough and aggressive political course concealed behind good intentions. Regular and occasional lexical synonyms are united into the construction of alternative semantics for enhancing the convincing effect of the utterance. Synonyms with positive connotation name those qualities of the American nation which, in the opinion of the state leader, supply the basis of its spiritual and physical superiority. Synonyms with negative connotation nominate those features which the nation considering itself to be great is not supposed to display to the world. Constructions with conjunctions of alternative semantics joining words which nominate political parties, or their members, emphasize the cooperation of Republicans and Democrats for solving important problems despite all their altercations. At the same time, the American presidents display a considerable difference in the usage of constructions with alternative semantics, which is determined by the extralinguistic factors, current social, economic, political tasks of the presidential administration. Thus, they occur in the speeches of Bush Sr. on the participation of the US troops in the war in the Persian Gulf. Clinton uses these syntactic structures to justify the interference into the conflict on the territory of the former Republic of Yugoslavia and to prove the necessity of improving the system of financial support for the impoverished population. In the speeches of Bush Jr., they serve to validate the military operation in Iraq, to confirm the inevitability of struggle with international terrorism and to show the negative aspects of embryonic stem cells research. With the help of these syntactic units, Obama tries to convince the audience in the inevitability of changes in the medical insurance and residence permit issuance, to protect the rights of sexual minorities and to restore diplomatic relations between the USA and Cuba. In Trump's addresses, they are aimed at showing the seriousness of the president's intentions to build the wall on the Mexican border and to carry out a number of reforms in order to make America great again. So, constructions with alternative semantics are regularly used in the institutional discourse of American presidents to instill certain ideas into the recipient's mind so that the audience would accept the political course necessary for the head of the state.
