WASHINGTON, May 8 (Xinhuanet) -- The US government plans to spend billions of dollars to replace or alter much of the anti-terrorism equipment installed after the September 11, 2001, terror attacks, which is now described as ineffective, unreliable or too expensiveto operate, US media reports said on Sunday.

    Although some of changes are being made because of new technology that has emerged in the past few years, many of them are planned because devices currently in use have done little to improve security, the New York Times reported on Sunday.

    Based on interviews with government officials, independent experts and a review of government documents, the report listed a number of problems concerning the current security systems, including radiation monitors at ports and borders that cannot differentiate between radiation emitted by a nuclear bomb and naturally occurring radiation from everyday material like cat litter or ceramic tile.

    The report also faulted postal service machines that test only a small percentage of mail and look for anthrax but not other biological agents.

    The defects in current security system can be partly traced back to the pressure the US government faced after 9/11 to move quickly to install monitoring tools to fence off possible new attacks. In some cases, agencies did not seek competitive bids or consider cheaper, better alternatives, and not all the devices were tested to see how well they worked, the report said.

    US homeland security officials said that they have already moved carefully to address some of the initial problems. In Nevada,for example, contractors are being paid to build prototypes of radiation detection devices that are more sensitive and selective.Similar competitions are under way elsewhere to evaluate new air-monitoring equipment and airport screening devices.

    In order to create a virtual shield around the United States, the US federal government will likely need to spend as much as seven billion dollars more on screening equipment in the coming years, according to government estimates. Enditem