Maura Harty, assistant secretary for consular affairs, said the State Department plans to test the high-tech passports by issuing them first to U.S. officials and diplomats.
But citing technological hurdles, she repeated a request that Congress postpone a looming deadline requiring 27 close U.S. allies to have similar passports in place by fall.
"Given the time that it has taken to resolve these technical, complex issues ... few of the visa waiver countries, if any, will meet the deadline," she said. "It is not a question of ill will. It is very much a question of difficult science."
On Monday, the House of Representatives voted to give visa-waiver countries a one-year extension on the deadline.
But Harty and Homeland Security Undersecretary Asa Hutchinson testified at a hearing of the Senate Judiciary Committee on Tuesday that it will take two years to perfect the technology.
"We have been told by almost all the countries that they cannot get it done within a year," Harty said.
Hutchinson said, "We believe that all countries can be compliant on November 30, 2006, and it should be a hard-and-fast deadline. It's important, I believe, for us to get this process right the first time."