Mamadou Tandja's supporters say he has brought economic growth
A trade union coalition has urged Niger's President Mamadou Tandja to scrap a planned referendum allowing him to seek a third term in office.
A civil servants' group warned of the dangers of social upheaval if the president went ahead with the vote.
However, thousands of his supporters held a rally in the capital Niamey on Sunday to back the plans.
Mr Tandja said on Friday night he would hold the vote, despite a ruling from the constitutional court against it.
He said he needed time to finish his projects - a huge uranium mine, setting up an oil refinery and a dam on the River Niger.
"President Tanja has secured jobs for thousands of youths," said one of his supporters, Alhaji Bashir Ahmed, on the streets of Niamey.
"He supports education. Tandja increased the price of our uranium, and soon Niger will sell oil. Therefore, there is no reason he cannot continue leading Niger."
'Setback for democracy'
But a coalition of opposition political parties and human rights organisations, Front for the Defence of Democracy (FDD), said it will disobey President Tandja if he calls a referendum before the installation of a new house of the parliament.
His second term of office is due to expire in December.
The US has also criticised plans to hold the referendum.
"We believe this risks undercutting Niger's hard-won social, political, and economic gains of the past decade, and would be a setback for democracy, based on the regular, peaceful transition of political power and faithful adherence to constitutional due-process," said state department spokesman Ian Kelly.
Mr Tandja, 70, dissolved parliament hours after the constitutional court rejected his plan to hold a referendum on extending his time in office.