Mexican poet Javier Sicilia and human rights activist Sergio Aguayo sent a letter to the dean of the Kennedy School of Government this week, saying that Calderon "does not fulfill the ethical standards" to work at the institution.

Aguayo and Sicilia, whose son was killed by drug traffickers in 2011, wrote that Calderon was responsible for the "human tragedy caused by this war: more than 60,000 dead, at least 25,000 people disappeared, 260,000 displaced."

Similar messages were posted on the petitions website www.change.org, which collected more than 30,000 signatures urging Harvard president Drew Faust to rescind the job offer.

Local radio said Calderon was heading to Harvard, his alma mater, on Tuesday.

The university announced in November that Calderon would give lectures and participate in academic life, touting him as a "vivid example of a dynamic and committed public servant, who took on major challenges in Mexico."

Calderon deployed the military after he took office in 2006 to crack down on the country's ultra-violent drug cartels, but the strategy was marked by a soaring death toll as gangs battled each other and security forces.

The new government of President Enrique Pena Nieto, who took office in December, says at least 70,000 people died during Calderon's six-year term.

Pena Nieto says his priority is to reduce the wave of murders afflicting Mexicans. He is creating a new federal police unit to combat cartels but he is keeping troops on the street until the force is ready.