President Mamadou Tandja changed the constitution to stay in power
Niger has reactivated arrest warrants against three exiled opposition leaders - including a former president.
The move jeopardises talks aimed at ending a crisis sparked when President Mamadou Tandja changed the constitution so he could stand for a third term.
Opposition delegates were taking part in talks because the government agreed to suspend the arrest warrants.
This week regional group Ecowas, mediating the talks, said it no longer recognised Mr Tandja's authority.
And on Wednesday the US suspended aid and announced it was imposing travel bans on senior officials.
Had he honoured his term limits, Mr Tandja would have stepped down as president on Tuesday.
No deal in sight
Minster of Justice Garba Lompo announced the arrest warrants would be activated for former President Mahamane Ousmane, former Prime Minister Hama Amadou and Mahamadou Issoufou, the leader of the main opposition party.
"From this day onwards all those people having warrants against them will be arrested if they come to Niger," said Mr Lompo.
The BBC's Idy Baraou, in Niamey, says few people expect the crisis talks to go any further.
He says the opposition wants to get rid of Mr Tandja at all costs, and now the government has struck back there seems to be no compromise on the horizon.
Opposition groups have described the president's move to stay in power in the uranium-rich nation as a coup.
But his supporters say he should remain as he has brought financial stability to one of the world's poorest nations.