Two years later, the budget shot up to $37 million, including $25.5 million for border security following the Sept. 11 attacks by al-Qaida. The aid included probes used for searching packages and looking behind ships' bulkheads, as well as "ion scanners" for sniffing out drugs or explosives.
Since then, the equipment sent to Mexico has gotten bigger and more expensive.
Recent donations include:
* Ten X-ray machines used by Mexican customs.
* Four Schweizer 333 helicopters, the first of a fleet of 28 that will be given to the Mexican Justice Department.
* Twelve UH-1H "Huey" helicopters, the first of 29 that the government is refurbishing and giving to Mexico.
* $13 million in computers, printers, communications lines and refurbishing of offices for Mexico's Federal Investigative Agency.
* Ten motorcycles and five trailers for Mexico's National Migration Institute and 12 Ford Lobo pickups.
This month, the U.S. Border Patrol taught water rescue techniques and gave equipment to authorities working on Mexico's border with Guatemala, the first time such training has taken place in Mexico.
Next year, the United States plans to give Mexico eight more helicopters and as many as six more X-ray scanners, three of which will go to Mexico's southern border with Guatemala.
The United States also plans to help Mexico with "installation of a telephone intercept capability," according to a State Department report. A department spokesman said that plans for phone-tapping equipment had been delivered but that the equipment had not been donated yet.
Meanwhile, Canada has gotten only one item from the United States since 2001: a 50-foot patrol boat used by the Royal Canadian Mounted Police in Vancouver.
Canada has fewer illegal immigrant crossings, and its police are better equipped than Mexico's. But its border with the United States is twice as long as Mexico.
At least one confirmed terrorist has tried to cross the U.S.-Canadian border: Ahmed Ressam, who was sentenced in July to 22 years in prison for plotting to bomb Los Angeles International Airport on New Year's Eve 1999. There have been no such cases on the U.S.-Mexican border.
The Pentagon is also taking a bigger role in Mexico under the banner of fighting terrorism, providing more money and training more soldiers, a development that worries many Mexicans. For decades, the Mexican government avoided any contact with the U.S. military. The distrust dates to the 1800s, when Mexico lost half of its territory to the United States through the Texan War of Independence and the U.S.-Mexican War. In 1914, the U.S. military invaded the city of Veracruz and occupied it for six months.
But in recent years, the Mexican government has forged a closer relationship with the United States under President Vicente Fox, a former Coca-Cola executive with conservative leanings.
"Mexico has changed in that area," Fox told The Arizona Republic in an interview aboard his presidential airplane in December. "Today, we have a new way of looking at sovereignty, and this in no way affects sovereignty."
As a result, the Pentagon earmarked $2.5 million this year for "foreign military financing" in Mexico. It is the first time in recent memory that Mexico has received direct aid from the United States for buying equipment.
The aid is aimed at "improving the capability of Mexican forces to respond to terrorist threats," a State Department report said, adding that it likely will go toward radar, communications and "detection" equipment.
The U.S. military has also begun training Mexican soldiers to fight terrorists and gather intelligence.
"The Mexican military has a bad record in this area," said Adrian Ramirez, president of the Mexican League for the Defense of Human Rights. "It's very worrying that the United States is turning to them for this."
The United States has long given free training to several hundred Mexican soldiers each year, but almost all the classes were in technical fields such as flight training or electronics repair.
But in late 2003, the focus changed. Of the 892 Mexican soldiers trained in fiscal 2004, 233 took classes under the new Counterterrorism Training Fellowship Program.
In 2005, the counterterrorism program spent $450,000 in Mexico. That's more than it spent in Colombia, a country that has been fighting a 41-year civil war against leftist guerrillas.