Federal government plans to use satellites to track trucks has been delayed because signals can be blocked or jammed, according to a report released last week. Planes, trains and ships also would be tracked under the plan.

The report by the Transportation and Defense departments said the problem with tracking cargo through a Global Positioning System is the satellite signals could be blocked or jammed by buildings or interference from other transmissions. Because of the delay, the plan will be pushed back to 2010, rather than 2008.