Jordan says it will not release an Iraqi female jihadist until it receives proof that a Jordanian pilot held by the Islamic State group is alive.

IS has threatened to execute the airman unless Jordan frees Sajida al-Rishawi by sunset on Thursday in exchange for Japanese hostage Kenji Goto.

"Jordan is willing to exchange Sajida al-Rishawi for the Jordanian pilot. At this point we want to emphasise that we have asked for proof of life from Daesh (IS) and we have not received anything yet," Jordanian government spokesman Mohammad al-Momani said.

"Rishawi is still in Jordan and the exchange will happen once we receive the proof of life that we asked for," he told reporters.

He made no mention of Goto.

The deadline set by IS to hand over Rishawi at the Turkish border in return for Goto's life falls when the sun sets in the Iraqi city of Mosul at around 1500 GMT on Thursday (0200 AEDT Friday).

Jordan has offered to free the Iraqi woman, who was convicted for her part in triple-hotel bombings in Amman in 2005 that killed 60 people, if IS releases their airman.

While IS threatened Kassasbeh's life, it was not clear from its message if the jihadist group was ready to free the pilot as part of an exchange.

Jordan has said its priority is to see the airman return home safely.

Kassasbeh was captured on December 24 after his F-16 jet crashed while on a mission against the jihadists over northern Syria.