The Islamic State in Iraq and Syria (ISIS) group has released a message purportedly by Japanese hostage Kenji Goto, extending the deadline for Jordan's release of an Iraqi would-be hotel bomber linked to al-Qaeda.

The audio recording, in English, says the Jordanians must present Sajida al-Rishawi at the Turkish border by sunset Thursday, or Jordanian pilot Lt. Muath al-Kaseasbeh will be killed.

The recording, distributed on Twitter by ISIS-affiliated accounts, appeared to be more rushed than two previous ones purportedly from Goto, which showed a photo of him along with the audio recording.

Thursday's recording contained only the audio, with an image of Arabic text that was an exact translation of the statement.

The Associated Press could not independently verify the contents of the recording.

The message comes as Jordan offered a precedent-setting prisoner swap to ISIS  in a desperate attempt to save al-Kaseasbeh who the militants purportedly threatened to kill, along with a Japanese hostage.

In Tokyo on Thursday, Japanese government spokesman Yoshihide Suga said the government was analyzing the latest message. He said Japan was doing its utmost for the release of Goto, working with nations in the region, including Turkey, Jordan and Israel.

"We are trying to confirm, but we think there is a high probability that this is Mr. Goto's voice," he said.

Suga refused comment on the specifics of the talks with Jordan, saying the situation was developing. The Cabinet was meeting to assess the latest developments.

King Abdullah reportedly gives assurances

Late Wednesday, the pilot's father met with Jordan's king who he said assured him that "everything will be fine."

King Abdullah II faces growing domestic pressure to bring the pilot home. However, meeting ISIS's demand for the release of a would-be hotel bomber linked to al-Qaeda would run counter to the kingdom's hard-line approach to the extremists.

An exchange also would set a precedent for negotiating with ISIS militants, who in the past have not publicly demanded prisoner releases.

Efforts to release al-Kaseasbeh, and Goto gained urgency with the release late Tuesday of a purported online ultimatum claiming the Islamic State group would kill both hostages within 24 hours if the al-Qaeda-linked prisoner was not freed.

By Wednesday evening, there was no word on the fate of the hostages and no sign a swap was underway.

Mideast Jordan Islamic State Japan

Jordanian pilot Lt. Muath al-Kaseasbeh, left, is being held hostage by ISIS. The group is calling for Jordan to release Sajida al-Rishawi, right, in exchange for the pilot. She was sentenced to death in Jordan for her involvement in a 2005 terrorist attack on a hotel that killed 60 people. (AP file photo)

Efforts to release the pilot and the journalist gained urgency with the release late Tuesday of a purported online ultimatum claiming ISIS would kill both hostages within 24 hours if the Iraqi woman was not freed.

Al-Momani said that "Jordan is ready to release the Iraqi prisoner, Sajida al-Rishawi, if al-Kaseasbeh is released unharmed." His comments were carried by Jordan's official Petra news agency.

Al-Rishawi was sentenced to death in Jordan for her involvement in a 2005 al-Qaeda attack on hotels in Amman that killed 60 people. Her release would be a major propaganda coup for ISIS.

Jordan is reportedly in indirect talks with the militants through religious and tribal leaders in Iraq to secure the hostages' release.

Pilot's family frustrated with government

The chairman of the foreign affairs committee of Jordan's parliament, Bassam Al-Manasseer, has been quoted as saying that Jordan and Japan would not negotiate directly with ISIS and would not free al-Rishawi for the Japanese hostage only.

Mideast Syria

Jordanian pilot Muath al-Kaseasbeh, centre in a white shirt, is pictured with members of ISIS. He was seized after his plane crashed near Raqqa in December. (Raqqa Media Center of the Islamic State group/Associated Press)

The pilot's father, Safi al-Kaseasbeh, has repeatedly criticized the Jordanian government's handling of the crisis, saying more must be done to bring his son home.

"I contacted the Turkish authorities after I found that the Jordanian government is not serious in the negotiations," he told The Associated Press, speaking after the government raised the possibility of a swap.

"The government needs to work seriously, the way one would do to free a son, like the Japanese government does," the father said.

The pilot's brother, Jawad al-Kaseasbeh, said the family is still "waiting for any word from the Jordanian government."

On Tuesday evening, about 200 of the pilot's relatives protested outside the prime minister's office in Amman, chanting anti-government slogans and urging that it meet the captors' demands.

'Please save Kenji's life'

In Tokyo, the mother of the Japanese hostage appealed publicly to Japan's premier to save her son. Junko Ishido read to reporters her plea to Japanese Prime Minister Shinzo Abe, which she said she sent after both Abe and Japan's main government spokesman declined to meet with her.

Mideast Jordan Japan Islamic State

Japanese Deputy Foreign Minister Yasuhide Nakayama is co-ordinating the hostage-release efforts with Jordan of freelance journalist Kenji Goto, held by ISIS. (Raad Adayleh/The Associated Press)

"Please save Kenji's life," Ishido said, begging Abe to work with the Jordanian government until the very end to try to save Goto.

"Kenji has only a little time left," she said.

The militants reportedly have killed a Japanese hostage, Haruna Yukawa, and the crisis has stunned Japan.

Although many in Japan are critical of the two men for going to Syria, Goto's friends and supporters have launched a social media campaign calling for his release.

Al-Kaseasbeh, 26, was seized after his Jordanian F-16 crashed in December near ISIS's de facto capital Raqqa in Syria. He is the first foreign military pilot they have captured since a U.S.-led coalition that includes Jordan began an aerial campaign against the Islamic State group in August.

This is the first time that the group has publicly demanded the release of prisoners in exchange for hostages. Previous captives may have been released in exchange for ransom, although the governments involved have refused to confirm any payments were made.

Goto, a freelance journalist, was captured in October in Syria, apparently while trying to rescue Yukawa, 42, who was taken hostage last summer.