Slovenia says it is considering building a border fence to help stem a record influx of migrants and refugees, as thousands more people arrived from Croatia on Friday.
The small Alpine nation has become the main entry point into the European Union's passport-free Schengen zone after Hungary sealed its southern borders with razor-wire fences to stop migrants desperately trying to reach northern Europe before winter sets in.
Prime Minister Miro Cerar said he hoped a mini-EU summit with Balkan and central European leaders on Sunday would help bring solutions to the crisis, but he has not ruled out a barrier along the 670-kilometre (415-mile) frontier with Croatia.
"We are considering that option too but at this moment... we are still looking for a European option," Prime Minister Miro Cerar told state TV late Thursday.
Ljubljana has asked Brussels for 140 million euros ($155 million, £100 million), in addition to police backup and logistical support.
"If on Sunday we do not get sufficient (grounds for hope), if we see there is no will for collaboration, then all possibilities will are available, seeing as we will have been left alone," Cerar said.
But he stressed that he saw the fence as a last resort.
"The border with Croatia is long and building a fence would be rather demanding. Police and army would have to guard it permanently to prevent illegal crossings," Cerar said.
More than 47,500 people have entered Slovenia, which has a population of just two million, since October 17 when Budapest shut its frontier with Croatia, barely a month after also closing its Serbian border.
Most of the migrants, mainly fleeing violence in Syria, Iraq and Afghanistan, want to get to Germany, the EU's economic powerhouse.
Some 14,000 were waiting in Slovenian refugee camps and registration centres on Friday morning, hoping to continue to neighbouring Austria whose Spielfeld border camp was also bursting with new arrivals.
Austrian Foreign Minister Sebastian Kurz on Friday warned the "surge into Europe" had become too big, adding that bloc members had a responsibility to protect their borders.
Border fences in Hungary and other EU countries had proven effective in tackling the crisis, Kurz said.
"The question is whether you want them or not," he told public broadcaster Oe1.
His comments echo those of Interior Minister Johanna Mikl-Leitner who on Thursday announced it was time for the EU to "build fortress Europe", after she had visited the Spielfeld checkpoint.
Around 7,000 migrants have crossed into Austria from Slovenia since Thursday, with some 4,500 still stranded at Spielfeld on Friday morning, police said.
Further down the migrant trail, 5,000 more people spent the night in freezing temperatures at Serbia's Berkasovo border crossing with Croatia, UN refugee agency spokeswoman Celine Schmitt told AFP on Friday.
People lit fires to warm themselves in the chilly morning fog, an AFP reporter said, while others looked for blankets, which appeared to be running short among voluntary aid workers. Children were crying inside small tents.
"So many children, (this is a) catastrophe," a Serbian police officer said.
Croatian Interior Minister Ranko Ostojic and his Serbian counterpart Nebojsa Stefanovic were to meet at the nearby main Batrovci border crossing later on Friday to discuss the situation at Berkasovo.