Countries in the Balkans have pledged to work together to prevent a repeat of the 2015 influx of migrants.
More than a million refugees crossed into Europe from North Africa and the Middle East, with many using the Balkans as a route into the EU.
Security and police officials from the region met in Bosnia on Thursday to discuss how to respond to a new smuggling route from Greece through Albania, Montenegro and Bosnia to Croatia and western Europe.
"We have to start implementing measures and we have to do it now while the situation is still under control," said Bostjan Sefic from Slovenia's interior ministry.
"Because if it gets out of control we will be faced with a big problem, especially the people who are on that migration route".
"We call on the action now, we need immediately to implement these measures to respond to the challenge," Sefic told reporters.
The border between Croatia and Bosnia is 1,000 kilometres long and around half of it is suitable for illegal border crossings.
Many gather in the Bosnian town of Velika Kladusa after travelling from places as distant as Syria, Iraq, Pakistan and Afghanistan.
Franz Lang, the head of Austria's Federal Criminal Police Office, said EU countries had discussed setting up "portal centres" in countries outside the EU, where requests for asylum would be processed.
"Egypt and Ukraine had been mentioned as potential countries," Lang said, adding he was not informed about the latest proposals.
"It's very important to try to prevent migrant routes from being long and dangerous, but to help people close to the source of migration."