It has been a trying week for Mexico-U.S. relations: a tense border confrontation between U.S. agents and apparent drug traffickers, a Mexican group's offer to print maps of the Arizona desert for illegal migrants and an exchange of terse diplomatic notes.

The administration of Mexican President Vicente Fox has its share of quarrels with other countries, but this promised to be one of the trickiest — involving the country's northern neighbor and largest trading partner at a time when the U.S. Congress is debating immigration reform.

For Mexico, migration to the United States is a mainstay of the economy; U.S. officials, on the other hand, see the issue in terms of national security and border safety.

"The situation is very sensitive, because the points of tension are very sensitive," said political scientist Oscar Aguilar Ascencio.

Not coincidentally, those issues have come to loggerheads just as Mexico enters the campaign season for its July 2 presidential elections.

Mexico's decision on Thursday to issue a diplomatic note asking U.S. Ambassador Tony Garza to stop making public comments about security and immigration issues may have more to do with domestic politics than anything else.

The note also demanded results in the investigation of the December shooting death of a Mexican migrant in California, which caused outrage south of the border.

"It's for internal consumption," Aguilar Ascencio said. "We're in an election year, and that's the context in which you have to view this."

The same context could apply to Foreign Relations Secretary Luis Ernesto Derbez's suggestion Thursday that uniformed men in a military-style Humvee who helped apparent drug traffickers escape back into Mexico earlier this week may have been U.S. soldiers or U.S. criminals disguised as Mexican troops.

As unlikely as that may be, it plays well for domestic audiences, Aguilar Ascencio said.

Not all the rhetoric has come from Mexican officials: Many here say U.S. proposals to build hundreds of miles of border walls are political grandstanding for a domestic audience, rather than a realistic solution to illegal immigration.

On Wednesday, Homeland Security Secretary Michael Chertoff condemned in "the strongest terms" plans by a Mexican governmental commission to distribute maps showing highways, water tanks and rescue beacons in the Arizona desert.

"This effort will entice more people to cross, leading to more migrant deaths and the further enrichment of the criminal human trafficking rings that prey on the suffering of others," Chertoff said.

The United States sent its own diplomatic note demanding an investigation of Monday's border incident in which the men dressed in military-style uniforms unloaded what appeared to be bundles of marijuana before setting fire to an SUV that bogged down in the Rio Grande as Texas law enforcement officers watched from the other side of the river.

Mexican leaders are eager not to be seen as backing down in the face of U.S. pressure. When Mexico "suspended" plans to print the migrant maps, it said it did so to avoid exposing migrants to American vigilantes, not because of U.S. criticism.

"We are not responding to that," said commission spokesman Angel Paredes. "We have not taken that into account."

Mexico may be relying on Washington to understand that it's election season here, and not to respond to the rising rhetoric.

"I don't think this is going to damage things very much," Aguilar Ascencio said. "There are interests at stake that are just too practical."

"I think what the United States is likely to do is not escalate the conflict," Aguilar Ascencio said. "Just take note ... and say 'That's fine, I understand.'"

"The Mexican government is obliged to do this song and dance," he said.