HOUSTON — Mexican President Felipe Calderón should order military troops back to the barracks and halt a losing war against drug cartels, a former Mexican foreign minister said Tuesday.“He should not have done it,” said Jorge Castañeda, who served in the Cabinet of Calderón’s predecessor, Vicente Fox. “He wasn’t prepared for it.”Castañeda, who was in Houston on Tuesday to promote his new book, said Calderón has framed his war on the cartels as a moral crusade, but it can’t be won, and can’t be continued after his successor takes office in 2012.“It is too costly. We are up to 42,000 dead,” he said. “By the end of Calderón’s term, more Mexicans will have died in this war than Americans in Vietnam.”As a condition of the retreat, Castañeda said cartels need to get the message that they must crawl back into the underworld, and stop the kidnapping, extortion and mayhem that have rocked Mexico for five years.If they don’t comply, the military needs to be unleashed again to go after them for the murder and mayhem, rather than wasting more resources on drug trafficking crimes, he said.“You don’t sit down with them. You don’t talk with them. You don’t pardon them,” he said of drug bosses.The cartels have fought against each other as well as against government security forces.Before Calderón took office, the military was used sparingly in the drug war, which was fought chiefly by civilian police.“It pretty much has to change; the next president will not be able to continue with Calderón’s policy,” he said.Legalizing drugs in Mexico is the only viable long-term solution, Castañeda said.Fox said the same thing when he was in Houston recently. “It went too far,” Castañeda said of Calderón’s war. “If Calderón hadn’t messed with it, maybe you wouldn’t have this reaction,” he said of high-profile Mexicans from across the political spectrum calling for legalization.“The question at the end of the day is whether the violence brought the war upon the country or whether the war brought the violence upon the country,” Castañeda said.He was in Houston to promote his new book “Mañana Forever? Mexico and the Mexicans,” which examines flaws in the national character that have prevented Mexico from realizing its democratic and social potential.