Washington (AFP) - More than a third of countries whose citizens can visit America without visas are failing to tell the US authorities about travelers' criminal histories and alleged links to terror groups, a government watchdog says.

Currently, 38 mostly European countries participate in the Visa Waiver Program, through which travelers can come to America for tourism or business for up to 90 days without obtaining a visa.

Those countries are supposed to share identity information about known or suspected extremists and share criminal history backgrounds.

"However, not all countries have shared information through the agreements," the Government Accountability Office (GAO) said in a report released Monday.

More than a third of countries are not sharing extremist identity information with the US Department of Homeland Security (DHS), and a similar number are failing to share criminal histories, it said.

Although those nations have other means of sharing such information with the US authorities, the DHS said the shortcomings are unacceptable.

"Thousands of Europeans have gone to fight in Syria and Iraq, and most of them are from countries that have visa-free access to the United States," Congressman Michael McCaul, chairman of the House Committee on Homeland Security, said in a statement Tuesday.

"These extremists are only a plane flight away from our shores, which is why overseas counterterrorism cooperation is critical."

Participant countries are adhering to the Visa Waiver Program's third requirement to report lost or stolen passports, however.

The US Congress passed a law in December to require Visa Waiver countries to fully implement information-sharing agreements in order to participate in the program, although the measure has yet to fully come into effect.

"I urge the Department of Homeland Security to implement that legislation aggressively," McCaul said.

Nearly 20 million travelers came to the United States under the Visa Waiver Program in fiscal year 2013, with admissions from each of the 38 countries ranging from around 700 to more than four million, the GAO said.

The agency did not specify which nations are failing to share information.