An effort to upgrade a key border enforcement system used by the U.S. Department of Homeland Security is seriously flawed -- and costing taxpayers millions of dollars with every delay.

A new Government Accountability Office report found multiple issues with how officials have been managing upgrades to the TECS program, which determines whether someone can enter the United States.

"After spending millions of dollars and over four years on TECS modernization, it is unclear when it will be delivered and at what cost,” according to GAO.

By 2015, TECS' annual licensing and maintenance costs are expected to be between $40 and $60 million.

TECS also helps prevent terrorism and provides "border security and law enforcement, case management, and intelligence functions for multiple federal, state, and local agencies," GAO said.

Sen. Tom Coburn, ranking member of the Senate Committee on Homeland Security and Governmental Affairs, said the GAO report "provides another illustration of how DHS spends more taxpayer dollars and gets less for the American people."