Volunteers in the US state of Arizona are preparing to carry out their own border patrols, as part of a campaign to highlight illegal immigration.
More people cross in Arizona since security was raised in California
After rallying in the town of Tombstone, the activists expect to deploy along the border to spot Mexican migrants entering the United States.
Critics say the patrols could spark vigilante violence.
More than 500,000 undocumented immigrants were arrested in Arizona last year.
The campaign's supporters say the Minuteman Project will highlight what they see as the federal government's failure to tackle the immigration issue.
At least 100 volunteers had registered by Friday afternoon for the campaign, a project organiser told the Associated Press.
The month of patrols is to begin on Monday.
Some of the volunteers plan to be armed.
The activists say they will report any border violations to the US authorities, rather than taking matters into their own hands.
"The newspapers and the TV cameras are hoping something will go wrong... or somebody will do something stupid," volunteer Robert Ordway said.
"That ain't going to happen."
The Minuteman Project has already strained international relations between Washington and its southern neighbour.
Washington accuses Mexico of not doing enough to stem the flow of illegal immigrants from across Latin America into the US, while Mexican officials condemn vigilante attacks near the border.
President George W Bush has so far delayed the implementation of plans announced in 2004 for a guest-worker scheme which would legalise the presence of immigrants.