Serbia's prime minister has warned of "huge problems" with migrants once Hungary's deploys military on its southern border with Serbia as part of a bid to stem the influx, and has urged the European Union to come up with a plan before that happens.

Aleksandar Vucic said Thursday that "no one knows what will happen" after Sept. 15 when Hungary's new measures against migrants and human traffickers take effect.

Vucic says Serbia is ready to share its part of the burden, but "we need to hear what would be that comprehensive solution."