Why did the US support the Chilean Coup against Allende in 1973?

The 1970s were times of great change in South America, with peasants and workers organizing for what they thought was a better life, looking up to communism. This was a severe threat to American corporate interests, and Salvador Allende, (Chile's President before the coup d'├ętat) was a socialist on the side of the workers.

Allende supported the strike of copper miners, and nationalized the copper mines. These were controlled by American corporate interests, and they did not take this threat lightly. Allende was also a strong supporter of Fidel Castro.

The US accused the Allende government of promoting Soviet interests in Latin America as Allende nationalized US companies. Investors from the US company International Telephone and Telegraph (ITT), who owned 70% of the Chilean Telephone Company (Chitelco) thought that the Chilean government would nationalize its assets there, and pressured ITT to put the US government through their connections and lobby groups.

Export income fell due fell in both production and price on international markets of copper, the most important export of Chile.

From Wikipedia: "Chilean politics ascended to a state of civil unrest amid strikes, lockouts, economic sanctions, CIA-sponsored propaganda, and a failed coup in June 1973".

There was a annual inflation rate of over 900%. Some people think Allende would have been overthrown by the Chilean army with or without US support.

According to the CIA, although they supported the military Junta, after the overthrow of Allende they had reservations about Pinochet being President. However, he ruled Chile for 17 years. Later it was recognized worldwide he was a brutal dictator and attempts were made to prosecute him in courts.

For further information check the declassified documents from the US Government in the George Washington University Webpage (See related links)