The Slovenian government has said soldiers are to help police manage the surge of migrants and refugees from Croatia.
Following an all-night meeting, a government statement said: "The inflow of migrants over the last three days has exceeded all manageable possibilities,"
The statement added that parliament would be asked to approve legislation allowing soldiers to help in the crisis "under very specific circumstances".
Under current law, the army can only provide technical and logistical support.
However, "this does not mean a state of emergency", Prime Minister Miro Cerar told journalists.
The parliament is to debate the legislation, and it may be in force within days.
Yesterday, more than 8,000 people entered the country from Croatia, with officials warning this largely exceeded its daily quota.
Slovenia also said today that it would ask the European Union to send additional police forces to its border with Croatia to help it deal with thousands of migrants streaming into the tiny country on their way to Austria and beyond.
"We need fast assistance of the European Union," President Borut Pahor told a news conference in Brussels after meeting European Council President Donald Tusk and EU chief executive Jean-Claude Juncker.
"Slovenia will formally ask for additional police forces to guard the border between Slovenia and Croatia and for financial help," he said.
The nation of two million people has become a new key transit point on the migrant trail, after Hungary sealed its Croatian border with a razor-wire fence to migrants on Saturday, just weeks after it had already shut its Serbian frontier.
Tens of thousands - many fleeing violence in Syria, Africa and Afghanistan - have been making their way from Turkey to the Balkans in recent months, hoping to reach Germany, Sweden and other EU states.
Slovenia criticised Croatia for lifting border restrictions at Croatia's border with Serbia last night, allowing the migrants who had been stranded in wet and muddy conditions for hours to trek to Slovenia.
Slovenia has called for greater European solidarity, warning it was "delusional" to expect small individual countries to handle the spiralling humanitarian crisis alone.
The Slovenian government also accused neighbouring Austria of capping its intake of migrants and only allowing in 2,000 yesterday.
Vienna has rejected the claim, saying more than 4,280 people had entered into Austria from Slovenia yesterday.