The US has vowed to stop every single illegal immigrant entering the country, by recruiting 1,000 extra agents and increasing the use of unmanned drones.
"Our goal is to gain control of our borders," said Homeland Security Secretary Michael Chertoff.
More than a million Mexicans are arrested every year as they try to enter the US to look for work.
Experts said the migration trend would continue because of the huge wage gap between the US and Mexico.
But Mr Chertoff insisted that once would-be immigrants learnt there was a high likelihood of being caught and sent home, the numbers trying to enter the US would fall.
In August, the civilian group Minuteman Civil Defence Corps angered immigrant rights advocates by starting to conduct its own border patrols.
Supporters of the Minuteman Project said they wanted to highlight what they saw as the federal government's failure to tackle the immigration issue.
The group's activities has strained relations between the US and Mexico.
Washington accuses its southern neighbour 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.
About 10 million of Mexicans live in the US and more than four million are said to stay illegally, BBC News reports.