Chad's Prime Minister, Nouradine Delwa Kassire Koumakoye, has said his country cannot absorb any more refugees from the Sudanese region of Darfur.
More than 200,000 refugees from Sudan are in camps in Chad
The UN says 12,000 people fled into Chad over the weekend after attacks on villages in Darfur by Sudanese forces pursuing rebel fighters.
"We are simply demanding that they be moved, otherwise we will do it," Mr Koumakoye said.
He accuses Sudan of being behind last week's failed coup attempt by rebels.
Mr Koumakoye, told reporters in the capital, N'Djamena, the international community should return the refugees to Sudan or move them elsewhere.
Sudan denies being behind the rebel assault on the capital last week, which Chadian forces repulsed.
Mr Koumakoye said: "We are being attacked by Sudan because of these refugees."
An estimated quarter of a million refugees live in camps near the Chad-Sudan border after fleeing the conflict in Darfur.
It's not clear whether the prime minister's comments represent a concrete change in policy, or a signal of Chad's growing exasperation with the situation along its border with Sudan.
The United Nations refugee agency, UNHCR, said if Chad decided on expulsions, there would be a real problem.
But a UNHCR spokeswoman in eastern Chad, Annette Rehle, told the BBC that she didn't believe refugees would be moved as local Chadian authorities were continuing to co-operate.
A French-led European Union peacekeeping force is scheduled to deploy to eastern Chad to improve security for the refugees, but it was delayed by the offensive by Chadian rebels.
The EU hopes to resume deployment in the next few days with an initial flight of logistics material.