Croatia got the green light on Thursday to join Europe's open travel zone, but Bulgaria and Romania were kept out because of opposition led by Austria over concerns about unauthorised immigration.
From 2023, people will not have to stop for border checks as they pass between Croatia and the rest of the so-called Schengen area - the world's largest free-travel area seen as one of the main achievements of European integration.
It will "shorten the journey and the wait, thank God," driver Nenad Benic said as he queued to cross the Bregana border point from Croatia into Slovenia on Thursday.
Romanian Prime Minister Nicolae Ciuca said he was disappointed and would apply to enter the zone again. "We regret and honestly do not understand the inflexible position taken by Austria," he said.
Bulgaria would also try again, its foreign minister said.
Croatia got the go-ahead to become the zone's 27th member after tense talks between the bloc's interior ministers in Brussels.
"To the citizens of Croatia: welcome, congratulations!," European Commissioner for Home Affairs Ylva Johansson, said.
"To the citizens of Romania and Bulgaria - you deserve to be full members of Schengen, to have access to the free movement... I share the disappointment with the citizens of Bulgaria and Romania."
Austrian Interior Minister Gerhard Karner said he had opposed Romania and Bulgaria because of security concerns.
"It is wrong that a system that does not work properly in many places would get expanded at this point," he said.
Austria, he added, had recorded 100,000 illegal border crossings so far this year, including 75,000 people who had not been previously registered in other Schengen countries as they should have been.
Accession needs unanimous backing from all members - 22 EU nations as well as Lichtenstein, Iceland, Norway and Switzerland.
The Netherlands also opposed granting access to Bulgaria, citing concerns over corruption and migration.
Immigration has been a hot button issue in Europe since 2015 when more than a million people arrived across the Mediterranean Sea, mostly on smugglers' boats, prompting the EU to tighten its borders and asylum laws.
U.N. data shows some 145,000 people have made the sea crossing this year while more than 1,800 perished trying to reach Europe's shores, numbers way lower than in 2015.
But the EU's border police Frontex said last month that 281,000 irregular entries had been recorded throughout the bloc in the first 10 months of 2022, up 77% from a year before and the highest since 2016.
With the Western Balkans route currently the most active, and the EU welcoming several million Ukrainians fleeing Russia's war, worries about immigration have returned to the fore.
(Reporting by Gabriela Baczynska, additional reporting by Bart Meijer and Clement Rossignol, Editing by Kirsten Donovan, Crispian Balmer and Andrew Heavens)
