MEXICO CITY — As Secretary of State Hillary Rodham Clinton arrives in Mexico, she needs to bring with her not only goodwill but a consistent U.S. position.

Former U.S. Ambassador to Mexico Jeffrey Davidow has compared Mexico to a porcupine because of the country's prickly nationalism, and right now its worst symptoms are on full display. After weeks of U.S. congressional hearings on Mexico's drug-related violence and front-page news stories focused on its many ills, the country is feeling badgered and bruised. Mexican President Felipe Calderon has even suggested that a concerted effort to discredit Mexico is taking place in the United States.

Mexico's quills are standing straight up, and Clinton will need to placate Mexicans with a good dose of public diplomacy. The best way to accomplish this goal would be to arrive with what has been lacking so far: a clear, unified message from President Obama's administration on the relationship it wants with Mexico.

Mexico's crime-related problems have become a focus of attention among lawmakers, law enforcement and the media in the United States. Over the past several months, there have been more than six congressional hearings, a segment on "60 Minutes" and numerous public statements made by key people in the U.S. intelligence community stressing Mexico's plight. While this attention is welcome — given the seriousness of the problems — a panoply of inconsistent, disjointed, contradictory stances has created ill will south of the border.

Mexico doesn't know whether it should pay more attention to those who advocate militarizing the border or to those who have come out against it. Mexico doesn't know whether the United States will make a concerted effort to stem the illegal smuggling of guns into its territory or whether the "right to bear arms" argument will shelve that issue. Members of the Obama team talk about a "strategic partnership," but then Congress ends a demonstration project to allow some Mexican trucks onto U.S. highways, as required under the North American Free Trade Agreement. Mexico then retaliates by placing tariffs on 90 goods affecting $2.4 billion in U.S. trade.

Mexico and the United States face a critical situation. U.S. efforts to help Mexico deal with drug trafficking and organized crime networks are not enough, and the problem is spilling into U.S. cities and streets, where consumption continues unabated.

Clinton should view the crisis as an opportunity to reframe the relationship and espouse the language of commitment and co-responsibility.

She should understand, as Mexican author Carlos Fuentes has suggested, that Mexico does not have a monopoly on drugs, bribes or corruption. And although Mexico has plenty to be criticized for, U.S. demand for drugs simply aggravates its neighbor's pre-existing institutional flaws and weaknesses.

Clinton undoubtedly will be greeted with open arms in Mexico if she brings with her a recognition of U.S. responsibilities; a willingness to reduce drug consumption north of the border; a commitment to disrupt financial flows and money-laundering that explain why Mexican drug chieftain Joaquin "El Chapo" Guzman is on the Forbes list of the world's richest people; a promise to limit the flow of high-caliber weapons across the border; and a disposition to accompany drug interdiction with a more comprehensive approach.

Denise Dresser, a contributing writer to the Los Angeles Times' Opinion section, is a columnist for the Reforma newspaper in Mexico City and a professor at the Autonomous Technological Institute of Mexico.