For nine years, Jesus, a Brooklyn baker, had no papers to prove his identity. An undocumented Mexican immigrant, he grew adept at living in the shadows, using friends’ library cards, stashing his money in his apartment, and stealing across the border when he returned from visiting his family. His fear of deportation is still as fierce as ever, but now he has something that makes him feel a bit safer: a Mexican consular identification card.

“I feel more secure,” Jesus said in Spanish, adding that of the Mexicans he knows in New York, “Almost everyone has one.”

The Mexican government has issued more than 2 million cards, and 11 states and more than 80 banks accept them as official identification. While undocumented Mexican immigrants still cannot get driver’s licenses from New York State, the consular identification cards, or matricula consular, as they are called in Spanish, lets them open bank accounts, board planes, and visit their children’s school. The cards makes no reference to the immigrant’s status. The laminated plastic card instead bears other identifying details such as name, local address, and date of birth.

“It’s huge in banking terms and it’s huge in terms of social or human benefits,” the consul general of the Mexican mission in New York, Arturo Sarukhan, said. “In banking terms, Mexicans are sending almost $14 billion annually to Mexico. That is 10% of their total income. The rest of the money, if it’s being channeled through a bank, is probably staying in a bank.”

Financial institutions from the Treasury Department to local banks have taken note of this potential windfall. The director of the Pew Hispanic Center, Roberto Suro, said the strongest support for the cards in America has come from financial agencies and institutions that “have a basic institutional interest in seeing money goes through legitimate, formal channels.”

While many banks, in Mr. Suro’s words, “thought you could put up a banner in Spanish and accept the matricula and you’d receive a stream of new clients,” the shift hasn’t been quite that dramatic. Most remittances continue to be transferred through wire services. Marketing campaigns designed to encourage immigrants to open accounts have, however, brought 400,000 new Latinos into the banking system, according to a Pew report issued last June. That’s about 5% of the estimated 8 million Latinos without access to banks here.

More than a half-dozen New York banks now accept the Mexican consular identification card. Citibank is the local leader in pursuing this business. The bank has launched an aggressive campaign aimed at New York’s Mexican community, creating financial literacy programs with local advocacy organizations, advertising on Spanish radio and television, and crafting banners showing a fictional Juan using a consular identification card to open an account.

Foreign governments, too, have taken note of the Mexican card’s success. With roughly 10 million undocumented immigrants in America, the consular identification cards are seen as a successful approach to protecting and monitoring their nationals living in this country illegally. Guatemala and Colombia recently launched programs modeled after the matricula, the Philippines has indicated its intentions to do so as well, and a dozen other countries from Chile to Pakistan have approached the Mexican government for information about its program.

Many federal and local officials are less sanguine, though. They warn that the cards are a step too close to normalization for immigrants residing illegally in this country, and that the IDs create a security risk. Critics, such as the secretary of homeland security, Tom Ridge, and top FBI officials, have said that even with Mexico’s security protections, such as a hologram and biometric information, the card can easily be forged.

While an August report by the General Accounting Office urged the federal government to provide consistent regulations, no new guidelines have been issued, according to Homeland Security.

“There is a real cognitive dissonance at the federal level over this,” Mr. Suro, of Pew, said.

At separate meetings with Latin American consular officials in November and December, New York City officials and Governor Pataki said they could not recognize the cards unless the federal government endorsed them. That was enough to stop the consulate of Argentina from distributing the cards at New York, even though Argentina’s Los Angeles consulate has issued cards since 2000. “We won’t do it until the city government or the New York Police Department or the state government gives us any hope that it can be recognized as an official ID,” an officer at the New York consulate, Ernesto Seman, said.

Officials of the Colombian government, in contrast, are considering expanding the card program to New York after being pleasantly surprised by the positive response to the cards among Colombians in Washington.

The significant difference between other countries’ interest in consular identification cards and Mexico’s is “sheer numbers,” Mr. Sarukhan said.

Mexicans make up far and away the largest group of undocumented immigrants living in America, with an estimated 3.5 million to 4.5 million. They are also probably the city’s largest undocumented immigrant group, with between one-quarter and one-third of the 750,000 Mexicans in New York State lacking legal status, a demographer, Jeffrey Passel, said.

In the three years since the Mexican government launched the card – a more secure version of an identity card that has actually been around for more than a century – the New York consulate has issued more than 81,000.

Initially, many members of the local Mexican community were fearful of revealing themselves to authorities, and the cards were distrusted. But the immigrants have rapidly grown to believe in the government’s stated commitment to preserving confidentiality. Now, demand constantly surpasses supply – the average allotment is 70 cards per day.

To secure a card for his wife, Jesus, the baker, got in line with her at the Mexican Consulate on East 39th Street at 2 a.m. Already more than a dozen people were waiting their turn to pay $27 for a consular identification card. By 8:30, when the daily rush began to flood the neighborhood and the Mexican woman selling tamales and arroz con leche had pushed her cart off, the block-long line had entered the consulate. Outside, Jesus remained, waiting patiently for his wife, Marlene.

When she emerged, it was without a card: The consulate had sent her home for additional proof of her address. Marlene remained determined. “You have a Social Security number,” she told the reporter. “For us the matricula is like that.”