"We're very worried about it," said Senator Sadot Sánchez Carreño.

Sánchez was one of five senators from Mexico's three main political parties who met with Arizona's attorney general, the state's top federal prosecutor, politicians, academics and the Arizona Hispanic Chamber of Commerce this week.

Hundreds of volunteers are said to be gearing up to patrol a 40 mile (65 kilometers) stretch of the border in southeastern Arizona 24 hours a day beginning April 1.

Members of the Minuteman Project say their mission is to stop the flow of illegal immigration, a job they say federal authorities are failing to do.

"We are American citizens who want to freely assemble under the First Amendment to express our displeasure with federal, state, and local appointees who have been charged with U.S. immigration laws and have left us wide open for another terrorist attack," said Jim Gilchrist, who is helping recruit Minutemen across the country.

Arizona is the most porous state along the United State's border with Mexico. The U.S. Border Patrol apprehended more illegal immigrants in Arizona during the fiscal year that ended Sept. 30, 2004, than were caught in California, New Mexico and Texas combined.

The number of immigrants crossing the U.S.-Mexico border typically peaks in April.

Hundreds of additional Border Patrol agents were sent to the state last spring, along with extra equipment, to try to curb the flow of illegal traffic.

The U.S. Border Patrol has expressed concerns about having the civilian patrols assist in its effort to choke off the flow of illegal immigration.

Some of the volunteers, many of whom are untrained and do not have experience with confronting illegal border-crossers, plan to arm themselves.

The Minutemen are only supposed to identify and follow illegal border-crossers and alert federal agents, Gilchrist said. They are not to interact with the immigrants, except to offer food, water or medical care.

The senators, who arrived Wednesday and leave Saturday, discussed their worries regarding the project with Paul Charlton, the U.S. Attorney for Arizona, and state Attorney General Terry Goddard.

"Mr. Goddard expressed his concerns that he doesn't want to see anything escalate, but he has very little jurisdiction in the area," said Goddard's spokeswoman Andrea Esquer.

Charlton said he discussed with the senators what federal law enforcement was authorized to do regarding the border.

"I told them that we need to balance the rights of individuals to say what they will and to associate with whom they want against the legitimate concerns for their own safety," Charlton said.

Charlton also said he told them that in the past fewer civilian border patrol agents have shown up at such events than were scheduled to attend.

Governor Janet Napolitano said she is concerned about untrained people coming to do a law enforcement function.

"People have a right to assemble it's a constitutional right to assemble but they do not have a right to take the law into their own hands," Napolitano said.