The US Reaction to Iranian Prime Minister Mossadegh's nationalization of the oil industry was to participate in his removal from power.

Upon being democratically elected, Prime Minister Mossadgegh started to make significant moves to nationalize the Iranian oil supply. This was in direct opposition to the British.  The American Secretary of State Dean Acheson remarked Mossadegh's nationalization efforts helped to spur a British approach that was "destructive, and determined on a rule-or-ruin policy in Iran."  British leaders soon employed the help of the United States.

Fearful that Mossadegh's nationalization of oil would move Iran closer to Soviet-style rule, American President Eisenhower supported the British plan to remove the Prime Minister from power.  In a letter written to Mossadegh about a month before the coup, Eisenhower displayed the US reaction to Iranian nationalization of oil reserves:

The failure of Iran and of the United Kingdom to reach an agreement with regard to compensation and handicapped the Government of the United States in its efforts to help Iran.  There is a strong feeling in the United Stats... that it would not be fair to the American taxpayers for the United States Government to extend any considerable amount of economic aid to Iran so long as Iran could have access to funds derived from the sail of its oil...

American reaction to Iranian nationalization was to recognize that its own interests were being threatened.  It is for this reason that American intelligence orchestrated and participated in the Mossadegh's removal from power.   Upon the declassification of documents that reflected such American involvement, President Obama said that "In the middle of the Cold War, the United States played a role in the overthrow of a democratically elected Iranian government."