The main reason why Hungary has not agreed to hand over the data is security concerns, he added.
"Such a request for someone to hand over the data of several hundred thousand of its citizens is unprecedented, countries do not do this. Every country protects and safeguards the data of its citizens with legal guarantees, Hungary does the same. Nowhere in the world do they hand over data of this amount, it is an unrealistic request, other countries do not do it either," Retvari told Hungary's Kossuth Radio.
"There are countries where dual citizenship is not allowed, and if we hand over this data and the authorities of these countries obtain these lists, very serious retortions will have to be applied to Hungarians, various procedures will have to be initiated, including criminal ones, at least in Zakarpattia [western region of Ukraine that prohibits dual citizenship]," the deputy minister said.
Hungary and the US have a different mentality, which sometimes overshadows the fact that the countries are allies, he added.
"You can see that in many cases, belonging to a different political camp and different world views — from the gender issue to migration and more recently wars — seem to outweigh the fact that the two countries are close allies," Retvari said.
On August 1, the US embassy in Budapest said that Washington had reduced the validity of entry permits under the Visa Waiver Program (VWP) for Hungarian citizens from two years to one year and limited them to a single use, citing security concerns over Hungary's simplified naturalization program.