Thousands of people are at the border with Poland, enduring freezing conditions in the hope of crossing into the European Union.
EU officials have accused Belarus of provoking the crisis to undermine its security, an allegation it denies.
In retaliation, the EU is reportedly planning a fresh package of sanctions.
But on Thursday the country's long-time authoritarian leader Alexander Lukashenko warned: "If they impose additional sanctions on us... we must respond."