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It is hard to remember a more important meeting between the president of Mexico and the United States.

U.S.-Mexico relations are at boiling point as both nations prepare for an Obama-Calderón summit meeting in Washington on Wednesday and Thursday that would include conversations on controversial issues such as Mexico's drug war, diplomatic cable leaks, the influx of U.S. arms and a wave of anti-immigration initiatives in the United States.

These issues are all taking a toll on the border nations relationship that had shown steady improvement in the recent years.

As President Felipe Calderón prepares for an official visit to Washington on Thursday to meet with President Barack Obama, frustrations have come out into the open and the rhetoric in some ways has regressed to the 1980s, when the two governments routinely traded barbs about drugs, money laundering, trade and investment issues.

The visit comes a little more than two weeks after the killing of U.S. Immigration and Customs Enforcement agent Jaime Zapata, who was shot to death on a highway in northern Mexico on Feb. 15 — with a gun that was smuggled in from the United States.

The killing brought back U.S. doubts about Mexico's ability to control violence, at the same time Mexico is beginning to chafe under what it sees as a lack of U.S. willingness to reduce its demand for drugs or stem the flow south of guns that fuel a conflict that has cost over 34,600 lives here since Calderón took office in 2006.

"As far as reducing the demand for drugs, they haven't done so ... as far as reducing the flow of arms, they haven't, it has increased," Calderón said in unusually harsh comments the week before the visit in an interview with the newspaper El Universal. "Institutional cooperation has been notoriously insufficient."

Calderón "has not gotten a response beyond rhetoric on the gun issue ... and I think he is bothered by the prospect that special interest groups in the United States have more influence than Mexico's entire leadership," said Raymundo Riva Palacio, a veteran columnist and political observer in Mexico City.

According to Mexican officials, the Calderón-Obama meeting was planned before the Zapata killing, and will focus on economic issues, anti-crime cooperation, and conditions for the estimated 12 million migrants living in the United States.

But Calderón's most important meeting may be with the new U.S. House Speaker, Republican John Boehner, according to Pamela Starr, professor of International Relations at the University of Southern California. It may be Mexico's best opportunity to defend the next phase of the $1.4 billion U.S. Merida Initiative anti-drug aid plan.

Calderón "wants to make sure they don't cut the funding for Merida, in their zeal to cut," Starr noted.

Contributing to the friction was the release of leaked cables written by U.S. Embassy personnel depicting Mexico's armed forces and police agencies as inefficient, corrupt, riven by infighting and "reliant on the United States for leads and operations."

Calderón's response was furious and, at times, personal.

The cables "have done a lot of damage with the stories they tell that are, in truth, distorted," Calderón said.

He objected to cables that talked about a lack of coordination among Mexican agencies. "I do not have to tell the U.S. ambassador how many times I meet with my security Cabinet, it is none of his business. I will not accept or tolerate any type of intervention," he said.

"But that man's ignorance translates into a distortion of what is happening in Mexico, and affects things and creates ill-feeling within our own team," Calderón said.

Calderón's office refused to say whether the "ignorance" remark referred specifically to U.S. Ambassador Carlos Pascual. The office said Pascual has met regularly with Calderón, despite local press reports suggesting Calderón was avoiding him.

Julian Ventura, Mexico's assistant secretary of foreign relations, denied reports of disenchantment and said the government had "a direct, intense relationship" with Pascual.

But the ambassador may have stepped on some toes in Mexico.

Calderón complained that "the ambassadors or whoever wrote these cables are pushing their own agendas." Riva Palacio noted there was a "self-congratulatory tone" in cables like the one sent after Mexican marines killed drug lord Arturo Beltran Leyva in a Dec. 2009 shootout.

"The impression they left was of a big celebration what 'we' (the United States) did," Riva Palacio said, despite the fact that Mexico has born the human and economic toll of the drug war.

Pascual may have also ruffled feathers in the government and the ruling National Action Party by dating the daughter of Francisco Rojas, the congressional leader of the former ruling Institutional Revolutionary Party, or PRI. Rojas' office and the U.S. embassy declined to comment on the issue.

"It can't help since she's the child of a PRI leader and Calderón is anti-PRI to the core of his being," said Starr. "Calderón will do whatever he can to defeat the PRI. He's convinced the worst thing that could happen to Mexico would be a return to the PRI."

In practice, the day-to-day contacts across the border between regulatory and law enforcement agencies, private companies and investors are immeasurably better than in the 1980s, when the U.S. suspected top Mexican officials of complicity in drug trafficking, money laundering or attacks on U.S. agents.

Things got so bad that in 1990 the DEA paid operatives in Mexico to kidnap and bring north a suspect in the 1985 torture-murder of DEA Agent Enrique "Kiki" Camarena.

But things changed. Mexico signed the North American Free Trade Agreement in 1994, the PRI lost its 71-year grip on the presidency in 2000, Mexico began extraditing record numbers of suspects and Calderón launched an offensive against the cartels in 2006.

The country has also opened to investment, inspection and regulation to such a degree that some U.S. agencies now operate what are essentially satellite offices here.

But while the United States wonders if Mexico can control violence and bring criminals to justice, Mexico has just been left wondering whether that opening is reciprocal.

Mexico continues to wait for the opening of U.S. highways to Mexican trucks, something it is entitled to under the 1994 North American Free Trade Agreement. The U.S. Congress has simply blocked that program under pressure from industry groups with arguments about highway safety.

And Mexicans have been angered at tough measures to crack down on illegal immigration in several U.S. states. They are especially alarmed about proposals that aim to deny citizenship to children of undocumented migrants born in the United States.

Two days before Calderón's visit, Mexico's Senate urged him to "express emphatically and categorically" Mexico's opposition to such measures in his meeting with Obama.

The Associated Press contributed to this article.

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