Since independence, the military has been the most powerful force in Honduras and if the coup goes unchallenged, it will show that it still has a veto on democratically elected presidents. Historically, that military has been supported unfailingly by the US. As US under-secretary of state Robert Olds wrote in 1927: "We do control the destinies of Central America and we do so for the simple reason that the national interest absolutely dictates such a course … governments which we recognise and support stay in power, while those we do not recognise and support fail."

US marines were sent to Central America over 30 times, and to Honduras seven times, between 1900 and 1934 to maintain order and quell any threat to the ruling oligarchies. With the introduction of Roosevelt's "Good Neighbour policy" in the 1930s, military intervention became less common; instead the US backed or installed "friendly dictators". In Honduras, the US smiled upon the brutal Tiburcio Carías Andino who ruled absolutely between 1931 and 1948, and a further series of military despots from 1951 to 1981.

Although democracy then returned to Honduras, the Reagan government poured in military aid, turning the fragile democracy into a militarised state. Using it as a base to pursue the war against the Nicaraguan revolutionary government, the US installed garrisons, supply dumps and air bases, as well as mercenary (Contra) training camps along the borders.

The US ambassador to Honduras at that time was John Negroponte, an ardent defender of the Honduran military, which was responsible for the "disappearance" of at least 184 people between 1980-92. He was one of a number of figures involved in the Iran-Contra affair who re-emerged in the George Bush administration. These old cold war warriors eyed with suspicion the new "radical populists" in Latin America, a term they used for the leftwing presidents of Venezuela, Bolivia, Ecuador, Nicaragua. They were disturbed by the leftist tendencies of Honduras's Zelaya and his friendship with the Venezuela's Hugo Chávez. It is not surprising that Chávez has called for an investigation into whether the CIA played a role in this weekend's coup.

Although it looks unlikely, given the history, these calls cannot be dismissed out of hand. The US military has a longstanding relationship with its counterparts in Honduras and the US maintains an airbase in Soto Cano today. Elements in the Pentagon have been concerned about the growing leftist trend in Latin America: a US Army War College publication in 2006, entitled US Military Priorities for Latin America, included in its list of security concerns "Implications of the rising threat of populism in the region" and "Implications of the return of the Latin American left". The government development arm, USAID, spends about $50m a year in Honduras on "promoting democracy", funding pro-US non-governmental groups and political parties.

But it is notable that Hillary Clinton and other state department officials have clearly condemned the coup. This is in stark contrast to the Bush administration's public support for the coup against Chávez in Venezuela in 2002. President Obama has said he is "deeply concerned". Obama needs to act urgently, with his Latin American neighbours and the Organization of American States (OAS), to ensure that the elected president is reinstated, and prove his country is no longer a friend of despots in its own backyard.