They also warned that Congress might have to legislate some changes in the program.
Senate Judiciary Homeland Security Subcommittee Chairman Jon Kyl, R-Ariz., and ranking member Dianne Feinstein, D-Calif., sent Chertoff a letter asking him to strengthen the visa waiver program by implementing recommendations from a Government Accountability Office report earlier this month.
"Certifying the integrity of the visa waiver program needs to be a top security priority for [the Homeland Security Department]," Feinstein said. The program lets citizens of 27 countries travel to the United States for tourism or business for 90 days or less without obtaining a visa.
Kyl said the government needs more information faster on travelers boarding planes so border officials can make informed decisions on whether they should be cleared. "Congress may need to alter the requirements of the program to ensure that visa waiver countries are giving DHS the data it needs to make those decisions," he said.
GAO found several weaknesses with the program. The department has not established adequate operating procedures for countries to report stolen or lost travel documents to the program and the International Criminal Police Organization (Interpol); and has not given U.S. border inspectors automatic access to Interpol's databases at primary inspection points, GAO said.
During a Sept. 7 hearing, department officials told the subcommittee they will issue reformed procedures for reporting data on lost and stolen passports in April, and begin giving border agents access to Interpol during primary inspection by next summer.
But Kyl and Feinstein wrote: "We consider that date too far in the future, and urge you to effect such changes immediately."
A Homeland Security spokesman insisted that the program has been improved.
"We've already addressed many of the issues that have been identified in the GAO report," the spokesman said Monday. "We continue close cooperation with visa waiver countries to share information on lost and stolen passports and to combat illegal immigration and terrorist or criminal threats."
The spokesman added that the department reviews its relationship with each participating country every two years.
In their letter, Kyl and Feinstein also asked Chertoff whether Congress should pass laws requiring countries to report lost and stolen travel documents to Interpol and to ensure that their citizens have a low-overstay rate in order to be allowed to participate in the program.
"The continued failure to implement fixes to these security gaps in a timely fashion is a risk we can no longer afford," Feinstein said. "The time to act is now."