Asked by journalists if Niger would turn Qadhafi's son over to Libya's new authorities, government spokesman Marou Amadou said, "No."
"With regard to (our) international obligations, we cannot send someone back there where he has no chance of receiving a fair trial and where he could face the death penalty," he said.
"On the other hand, if this gentleman or any other person is wanted by an independent court ... which has universal competence over the crimes for which he is pursued, Niger will do its duty," he added.
On a visit to Libya on Thursday with British Prime Minister David Cameron, French President Nicolas Sarkozy said he was confident that Niger would cooperate in this regard.
"We have no reason to doubt the Nigerien leaders' commitment to international justice," Sarkozy said.
"We are a sovereign government and we shall consider requests or demands when they are received," said Amadou.
Saadi Qadhafi is on a list of people close to the Qadhafi regime targeted by UN Security Council travel sanctions.
The 38-year-old, the third of Qadhafi's seven sons, renounced a football career in Italy in 2004 to join the army, where he led an elite unit.
He arrived in Niger, one of the west African countries that benefited the most from Qadhafi's largesse, on Sunday in a convoy alongside other members of the toppled regime.
Niger has confirmed it has 32 Qadhafi loyalists on its soil, including three generals, saying it allowed them entry for "humanitarian reasons".
Niamey has officially recognised the National Transitional Council as Libya's interim leadership.
It has insisted that Qadhafi himself was not on its territory and declared that it will comply with international agreements should wanted Libyans cross into its borders.
"Niger will not hesitate to respect its engagements, as a democracy and lawful state," Amadou said.
The Qadhafi loyalists are "under our guard, our surveillance and our control" and the government "will be making sure that these people refrain from all political activity," he added.
The spokesman said an NTC delegation was expected in Niamey and in the meantime it was in regular contact with the transitional authority.
"The worst (thing) is not some Libyan refugees close to Qadhafi, but the extremely serious complication that this (Libyan) war is having on the security and stability of the already fragile Sahel" region, he said.
"People have to look at the real problems in this Libyan crisis: it is reinforcing AQIM, reinforcing drug traffickers for whom the Sahel, all six million square kilometres, is a refuge," Amadou said.
Copyright AFP (Agence France-Presse), 2011