Slovenia has been struggling to cope after suddenly finding itself last month on the main route for thousands of migrants travelling to northern Europe after Hungary sealed its borders.
Police figures at around midday (1100 GMT) showed 149,464 people had entered the small central European country from Croatia since Hungary closed its border on October 17, diverting the flow westwards.
All but a handful of them travel through Slovenia heading for Austria and beyond.
President Borut Pahor told parliament on Thursday that Slovenia would "proportionally tighten" border controls if Austria moved to restrict entry, something he believes is "likely".
Austria's Interior Minister Johanna Mikl-Leiter said last week that Vienna wanted to strengthen the border with Slovenia, although it remains unclear what form this might take.
If Austria -- which expects a record 85,000 asylum claims this year -- were to erect a fence, it would be the first such barrier between two countries in the passport-free Schengen zone.