The father of a Jordanian fighter pilot and the wife of a Japanese journalist held by the Islamic State in Iraq and Syria (ISIS) pleaded for their loved ones' lives after a possible prisoner swap wasn't carried out by a deadline of sunset Thursday.

The extremists had demanded that Jordan release a female al-Qaeda prisoner from death row, and they purportedly threatened in an audio message to kill the airman if she was not freed by the deadline.

After sundown in the Middle East, there was no word on the fate of Lt. Muath al-Kaseasbeh and journalist Kenji Goto, and the families' agonizing wait dragged on.

"We received no assurances from anyone that he is alive," Jawdat al-Kaseasbeh, a brother of the pilot, told The Associated Press. "We have no clue about where the negotiations stand now. We are waiting, just waiting."

The possibility of a swap was raised Wednesday when Jordan said it was willing to trade Sajida al-Rishawi, the al-Qaeda prisoner, for the pilot.

However, the audio message purportedly posted by ISIS only said the pilot would be killed if al-Rishawi was not delivered to the Turkish border by the deadline. There was no mention of Goto and no word on whether the pilot would be traded for the woman. The authenticity of the recording could not be verified independently by the Associated Press.

Jordan wants proof pilot is alive

On Thursday afternoon, Jordan's government spokesman, Mohammed al-Momani, signalled that, in any case, a swap was on hold because the hostage-takers had not delivered proof the pilot is still alive.

Al-Rishawi, 44, faces death by hanging for her role in a suicide bombing, one of three simultaneous attacks on Amman hotels in November 2005 that killed 60 people. She survived because her belt of explosives didn't detonate. She initially confessed, but later recanted, saying she was an unwilling participant.

Al-Rishawi, who is from the Iraqi city of Ramadi, has close family ties to the Iraqi branch of al-Qaeda, a precursor of ISIS. Three of her brothers were al-Qaeda operatives killed in fighting in Iraq.

Mideast Jordan Islamic State Japan

Jordan has offered to exchange Lt. Muath al-Kaseasbeh, left, for Sajida al-Rishawi, an Iraqi woman sentenced to death in Jordan for her involvement in a 2005 attack on a hotel that killed 60 people. (AP file photo)

Jordan has faced tough choices in the hostage drama.

The release of al-Rishawi, involved in the worst extremist attack in Jordan, would run counter to the government's tough stance on Islamic extremism.

However, King Abdullah II is also under domestic pressure to bring the pilot home. Jordan's participation in U.S.-led airstrikes against ISIS in neighbouring Iraq and Syria is unpopular in the kingdom, and the pilot is seen by some as the victim of a war they feel the country shouldn't be involved in.

The pilot's relatives have also expressed such views and have accused the government of bungling efforts to win his freedom.

After the deadline passed, al-Kaseasbeh's father, Safi, urged his son's captors to have mercy on a fellow Muslim and spare his life, saying "amnesty is an Islamic value."

The pilot's family is from the tribal area of Karak in southern Jordan, and the elder al-Kaseasbeh spoke at a "diwan," or meeting place, for Karak tribesmen in the Jordanian capital of Amman.

Dozens of protesters chanted slogans as a former army chief arrived at the diwan. "They abandoned Muath, the son of the army!" they shouted. "Why are we fighting outside our borders?"

1st foreign military pilot captured by ISIS

Al-Kaseasbeh was seized after his Jordanian F-16 crashed in December near ISIS's de facto capital of Raqqa in Syria. He is the first foreign military pilot to be captured since the U.S. and its allies began striking ISIS more than four months ago.

In Tokyo, Goto's wife, Rinko Jogo, made her first public appeal for her husband's life, saying she had not spoken out previously because she was trying to shield their daughters, a newborn and a two-year-old, from media attention.

She revealed that she exchanged several emails with her husband's captors, and that in the past 20 hours she received one that appeared to be their final demand.

"I fear that this is the last chance for my husband, and we now have only a few hours left," she said in a statement released Thursday through the Rory Peck Trust, a London-based organization for freelance journalists.

She urged the Japanese and Jordanian governments to finalize a swap that would free both hostages. "I beg the Jordanian and Japanese governments to understand that the fates of both men are in their hands," she said.

The hostage drama began last week with the release of a video by ISIS showing Goto and another Japanese hostage, Haruna Yukawa. They were kneeling in orange jumpsuits beside a masked man who threatened to kill them in 72 hours unless Japan paid a $200 million ransom. That demand has since apparently shifted to one for the release of al-Rishawi.

The militants have reportedly killed Yukawa, 42, although that has not been confirmed.

Any swap with the militants would set a precedent for dealing with the hostage-takers. The group has not publicly demanded prisoner releases before. Other captives may have been freed in exchange for ransom, although the governments involved have refused to confirm any payments were made.