By Stephen Gibbs
BBC News, Mexico City
Mexico and the US have talked of a new era of cooperation
The other day, a Western diplomat based in Mexico City made a small confession to me.
"If only I knew the pain, heartbreak, and destruction which the drug trade caused," he said, "then I would never have smoked so much of the stuff at college".
It is tempting to see the dramatic change of attitude by the US administration towards Mexico's drug trade in similar terms.
For years the United States - although providing the consumers which have made Mexican drug-runners rich and selling most of the weapons which have made them such a formidable force - have not seemed to have seen the issue as a priority.
It was viewed as a problem that stopped on the southern side of the border.
All that crossed was a sufficient supply of cocaine, marijuana and methamphetamines - the experimental consumption of which is almost a rite of passage for many American students.
But the brutal inter-cartel violence in Mexico, which has burst onto America TV screens over the last few months, seems to have had a profound effect on this administration.
Last month, as she travelled south from Washington to Mexico City, Secretary of State Hillary Clinton went to the back of the plane and made some surprising remarks to the journalists travelling with her.
"Our insatiable demand for illegal drugs fuels the drug trade," she said.
"Our inability to prevent weapons from being illegally smuggled across the border to arm these criminals causes the deaths of police officers, soldiers and civilians."
Never had a senior American government official described the role of the United States in the trade in such terms.
Those close to US President Barack Obama have stressed that the reason he is coming to Mexico City is to stress his support for President Felipe Calderon in his war on drugs.
Both governments talk of a new era of co-operation, of shared responsibility.
Drug violence has shocked Mexico. Gory images of murders and decapitations can be seen on the front covers of newspapers every day.
Many Mexicans despise that fact that a culture of organised crime pervades society. Kidnapping rates have soared.
But ask people in the capital what they hope from President Obama's visit and you get a reminder that there is a lot more to the US-Mexico relationship than drug cartels and weapons smuggling.
Most seem far more pre-occupied with another American export - the recession.
"Let's hope that Obama and Calderon can energise the economy because it is affecting us too much," said Juan Sanchez, as he breakfasted on tacos at a street market in the la Condesa neighbourhood.
Mexico sends 80% of its exports to the United States. Millions of Mexicans depend upon remittances from their relatives working in the US. The downturn is being felt here.
Jose Cappon runs one of the hundreds of small businesses in the capital which supply American auto manufacturers. His company makes plastic hub caps for Ford. Last year he had 70 employees. Now he has just 11.
"When things go well, maybe they will look again to Mexico," he says, standing in front of a dormant plastics moulding machine.
"But right now, the main thing for Americans, is America."
Not everyone looks set to suffer in Mexico's recession.
History has shown that drug consumption tends not to fall significantly in economic downturns.
"Drug traffickers can take advantage of the crisis," says Professor Jorge Chabat, from Mexico City's centre of research and teaching in economics.
"It is a good time for doing business if you have cash. And these guys have cash."