Technical problems have forced the Bush administration to retool a high-tech virtual fence along the U.S.-Mexico border and will delay the first phase for at least three years, the Washington Post reported on Thursday.

There are an estimated 12 million illegal immigrants in the United States, many from Mexico. Immigration is a highly charged topic and a major issue in the campaign for November's presidential election.

Department of Homeland Security officials and congressional auditors told lawmakers on Wednesday that problems found in the 28-mile pilot project built near Nogales, Arizona, by Boeing Co. will require a change in plans, the Post reported.

Homeland Security Secretary Michael Chertoff had announced on Friday, during a review of border-control efforts, that the so-called Project 28 was finally ready for service in efforts to stop illegal crossings.

The $20 million project of sensor towers and advanced mobile communications was supposed to be completed in mid-2007 but had been delayed by software problems.

The surveillance system was designed to complement a planned 700-mile (1,130-km) border fence that has drawn opposition along its route.

While the Department of Homeland Security took over the high-tech project from Boeing last week, authorities confirmed the initial deployment did not work as planned or meet the needs of the U.S. Border Patrol, the Post said.

The newspaper quoted the department official responsible for border security, Gregory Giddens, as saying: we ... have delayed our deployment as we work through the issues on Project 28. While there is clear urgency of the mission, we also want to make sure we do this right.

The Post report cited congressional investigators saying that, because of the new troubles, the first phase will not be completed until near the end of the next president's first term.

Republican presidential front-runner Sen. John McCain of Arizona is fighting conservative criticism that he has been too soft on illegal immigration.

The Democratic candidates, New York Sen. Hillary Clinton and Illinois Sen. Barack Obama, accuse the Bush administration of heavy-handed tactics.

Giddens told the Post construction of the physical fence was costing about $4 million per mile but that the Department of Homeland Security hoped to cut the average cost to $3 million per mile.

President George W. Bush's 2009 budget contains no funds to add fencing beyond the 700 miles meant to be completed this year, the paper said.

The total cost is not known, the Post said Richard Stana, the Government Accountability Office's director of homeland security and justice issues, told the lawmakers.

Stana said this was because Department of Homeland Security officials do not yet know the type of terrain where the fencing is to be constructed, the materials to be used or the cost to acquire the land.

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