* Kidnappers give France ultimatum over 2 foreign hostages
* Kidnappers threaten to kill aid workers if demands unmet
* One of the captive aid workers says being well treated
(Adds comment from Zoe's Ark leader)
By Alastair Sharp and Khalid Abdel Aziz
KHARTOUM, April 12 (Reuters) - Kidnappers holding two aid workers in Sudan's Darfur region said on Sunday they will kill them unless Paris retried members of a French group convicted but later pardoned over the abduction of children from Chad.
An unnamed member of a group holding the two female aid workers captive and calling itself the Freedom Eagles of Africa also threatened to target French interests in Sudan, Chad and the Central African Republic if their demands were unmet.
Stephanie Joidon, a Canadian, and Claire Dubois, a French national, working for Aid Medicale International (AMI) were seized at gunpoint from their compound in the south Darfur settlement of Ed el Fursan on April 4.
"We demand France open the case of the Zoe's Ark criminals and judge them through a fair court," one of the abductors told Reuters by telephone.
"If the French government is not serious in negotiations with us and does not respond to our request, we will kill the two aid workers," he said.
Six members of humanitarian group Zoe's Ark were jailed in 2007 for trying to fly children, aged between one and 10, out of Chad to Europe. Chad said they had no authorisation to take the children out of the country.
The six, who denied the charges, were sentenced to eight years' hard labour by a Chadian court, but were pardoned in March 2008 by Chadian President Idriss Deby.
Joidon, who was allowed by the kidnappers to speak to Reuters, said she and Dubois were being treated well.
"We are OK, we have food and water and they are correct with us, but we can't wait to go home," she said.
READY FOR RETRIAL
The French foreign ministry declined to comment on the case.
Eric Breteau, the leader of the Zoe's Ark group who lives in France, said he was ready to return to court if that would help. "If a trial of Zoe's Ark can help matters, I'm up for it," he told Reuters by telephone, adding that he hoped a new hearing would cast light on where the children actually came from.
Breteau has always maintained that the children had escaped from Darfur and needed help. "There isn't the slightest proof that the children came from Chad," he said.
AMI said on Sunday it was leading negotiations to free its staff but declined to give details "given the delicate nature of the affair and out of respect for the families concerned".
Tensions have risen in Sudan since the International Criminal Court issued an arrest warrant for Sudanese President Omar Hassan al-Bashir over alleged war crimes in Darfur and Bashir ordered the expulsion of 16 aid groups.
Last month, four members of aid group Medecins Sans Frontieres were held for three days by a group that, Sudanese government officials said, was protesting against the warrant.
Before the two incidents, kidnappings of foreign aid workers in the Darfur region were rare.
Land around Ed el Fursan, about 90 km (55 miles) southwest of the South Darfur capital Nyala, has seen an upsurge of fighting in recent weeks between members of the rival Habbaniya and Fallata tribes.
The clashes, rooted in long-standing disputes over land and other traditional rights, have escalated because of the supply of arms that has flooded in during the six-year Darfur conflict. (Additional reporting by Crispian Balmer and Gregory Blachier in Paris; Editing by Katie Nguyen)