BRUSSELS - The extension of the European Union's border-free travel zone to nine new members on Dec. 21 will bring strong economic and political benefits, Slovenia's interior minister said on Thursday.

People from the Czech Republic, Estonia, Hungary, Lithuania, Latvia, Malta, Poland, Slovakia and Slovenia will be able to travel to and from the existing 15 members of the so-called Schengen area without having to show their passports.

"It's a very key step for the people. They will really feel after the enlargement of Schengen that they are part of the EU because they can travel freely without controls at the borders, and that is one of the basic ideas of the EU," Dragutin Mate told Reuters in an interview.

EU interior ministers on Thursday agreed the move, which will dismantle border posts between most "old" and "new" member states.

"It's not only for travelling. I strongly believe ... in local areas the economy will start growing better and better, and usually the areas around borders are not well developed. They will now have a new push," Mate said.

Thirteen EU countries, plus Norway and Iceland, are currently part of the Schengen area whose members apply common external border controls and a common visa policy, and share a police database on criminals and lost cars.

Britain and Ireland have chosen not to join.

The nine countries that will join "Schengen-land" next month became members of the now 27-nation EU in 2004. Cyprus, which joined at the same time, has asked for one year's delay.

Mate said the suppression of border controls would make a considerable difference in countries where people had faced tough military controls during the Cold War.

Mate said it was hard for Slovenians to understand why they would still have checkpoints at borders with Croatia, which is not an EU member.

"For centuries the border between Slovenian territory and Croatian territory was (only) administrative," he said. This changed after both countries became independent.

Romania and Bulgaria, which joined the EU only this year, need to do more work to meet security criteria, officials say.