WASHINGTON — The U.S. State Department plans to improve technology that will be embedded in new U.S. passports after recent tests revealed that information in the documents could be vulnerable to ID theft.

Frank Moss, the State Department's deputy assistant secretary for passport services, said the agency will include new high-tech security features that will minimize the risk of identity theft, even if the change delays plans to start issuing the passports to new applicants later this year.

The agency's decision was a small victory for civil libertarians and privacy groups who for years had warned the State Department that its plans to embed passports with radio frequency identification (RFID) technology were flawed. Travel groups and some European countries also warned about security vulnerabilities.

Radio-frequency ID devices, known within the tech industry as "contactless smart cards," are used in many employee ID cards that are passed over an electronic reader for entry to a building or passage through a turnstile. The passport chips will store information about passport holders and will contain digital photographs enhanced with face-recognition technology.

The radio-frequency chips will transmit data from the passport to electronic readers at U.S. airports and border crossings. The problem, some privacy activists say, is that thieves could use commercially available handheld readers to surreptitiously intercept the data on passports, identifying Americans overseas and stealing their information.

Moss had said that there was only a slim chance that data on passport chips could be read from more than four inches away. Recent tests conducted by the National Institute of Standards and Technology concluded that he was wrong, he said. "We admit the chip, with a more powerful reader, can be read at a distance of 24 inches," Moss said.

The agency now plans to include metal inside U.S. passport jackets that will help shield the chip from being read by anyone except U.S. Customs agents.