Alarmed by large-scale spying on their state-owned oil and mining firms and monitoring of personal communication of their top leaders and bureaucrats by the U.S. National Security Agency (NSA), South America’s two biggest countries are urging all other countries in the region to form a joint cyber shield to deflect such surveillance. The move, led by Brazil and Argentina, is the first such effort by a group of countries since NSA revelations about mass surveillance began to come out in June.

In a crucial meeting in Brasilia on Friday, Argentine Defence Minister Agustin Rossi met his Brazilian counterpart, Celso Amorim, and the two leaders agreed to incorporate all the 12 countries in the continent, which together form the UNASUR (Union of South American Nations), in their bilateral treaty on cyber defence.

In August, when top-secret documents released by NSA whistleblower Edward Snowden had revealed that Brazil was one of the most-monitored countries by U.S. intelligence agency, the two ministers had met in Buenos Aires to discuss how to jointly fight the existing and potential cyber threats — mostly coming from the North.

On Friday, the two countries decided to take their cooperation to the next level. “I think that the UNASUR bloc has a common defence strategy,” said Mr. Rossi after his meeting with Mr. Amorim. “In order to preserve the region’s progress, we should consider this policy,” he added.

A series of stories in Brazilian media in recent months have revealed massive communications surveillance on Brazil, including the email and personal phone of its President Dilma Rousseff. A similar pattern targeting Argentina too has come to light. Angered by the revelations, >Ms. Rousseff cancelled a state visit to Washington and also took the Obama administration to task at the U.N. General Assembly session in September 2013.

In July 2013, espionage by U.S. agencies also took centre-stage in the region when Bolivian >President Evo Morales’ aircraft was forced to land in Austria because of suspicion it carried Mr. Snowden. At that time, Brazil, Argentina and other countries had agreed that it was a provocation aimed at all of South America.

Though it’s Brazil and Argentina which are keen to form a cyber shield that covers the whole continent, according to sources, they are likely to get support from Venezuela, Bolivia, Uruguay, Chile and Ecuador. The UNASUR Defence Council is likely to meet soon and define joint actions regarding cyber security in the region.

After the Friday meeting, Mr. Amorim said that the Council, which has not met since the NSA documents were revealed by Snowden, would be debating the issue in the next meeting. “However, while we wait until joint decisions are made in the South American sphere, we can work bilaterally as we are doing with Argentina,” he added.

Even as they urge other countries to join the common shield, Brazil and Argentina have already started working on a joint cyber command. Argentina will soon send a group of military officers to Brazil Superior War Academy to train in “cyber-war”, while

Brazilian officers will travel to Buenos Aires to train at the Army’s University Institute.

On Friday, Mr. Rossi was also invited to visit the Brazilian Army’s Communications and Electronic War Centre to learn about the defence actions carried out in Brazil. Mr. Rossi and Mr. Amorim did not detail any other measures that both countries will be taking on jointly.

But Mr. Amorim said that if UNASUR does not act on this issue, then Brazil and Argentina will be obliged to bi-laterally act. Both countries have already signed a military agreement about sharing defence techniques against cyber warfare.

In recent months, Brazil has taken a number of steps to counter the espionage by NSA. In addition to making a law that will make it mandatory for all tech firms like Facebook and Twitter to save their data locally, the country is also working on a global conference on internet governance in April 2014.