People walk past television screens displaying a news program, about an ISIS video showing Japanese captive Kenji Goto.

An audio message purportedly from a Japanese journalist being held by Islamic State of Iraq and Syria militants said a Jordanian air force pilot also held by the group would be killed unless an Iraqi female prisoner in Jordan was released by sunset on Thursday.

The message appeared to postpone a previous deadline set on Tuesday in which the journalist, Kenji Goto, said he would be killed within 24 hours if the Iraqi was not freed.

The latest audio recording, which could not be verified, was posted on YouTube early on Thursday.

Japanese Prime Minister Shinzo Abe said Thursday that Tokyo was analyzing the authenticity of the video.

“We are aware of the new message,” Abe said during a parliamentary session. “Now, we are verifying (its authenticity), but we will do our best to secure the release of the Japanese national as soon as possible,” he added.

Japanese Chief Cabinet Secretary Yoshihide Suga told a news conference that chances were high it was Goto’s voice in the recording.

“I am Kenji Goto. This is a voice message I’ve been told to send to you. If Sajida al-Rishawi is not ready for exchange for my life at the Turkish border by Thursday sunset 29th of January Mosul (Iraq) time, the Jordanian pilot Muath al-Kasaesbeh will be killed immediately,” the voice in the recording says.

Jordan said on Wednesday it had received no assurance that al-Kasaesbeh was safe and that it would go ahead with a proposed prisoner swap only if he was freed.

The audio tape message implied that the Jordanian pilot would not be part of the exchange deal, indicating any swap would be between Goto – a veteran war reporter – and al-Rishawi. Any swap that left out the pilot would not go down well with the public in Jordan, where officials have insisted he is their priority.

There was no immediate comment from Jordanian government officials, but a security official said the authorities were trying to verify the authenticity of the recording and were coordinating with their Japanese counterparts.

On Tuesday, a video was released purporting to show the Japanese national saying he had 24 hours to live unless Jordan released al-Rishawi, an Iraqi woman on death row for her role in a 2005 suicide bomb attack that killed 60 people in the capital Amman.

Jordanian government spokesman Mohammad al-Momani said earlier that Jordan was ready to release al-Rishawi if Kasaesbeh was spared, but made clear that she would be held until the pilot was freed.

Kasaesbeh was captured after his jet crashed in northeastern Syria in December during a bombing mission against Islamic State, which has captured large tracts of Syria and Iraq. He is from an important Jordanian tribe that forms the backbone of support for the Hashemite monarchy.

The Jordanian comments have raised concerns in Japan that Goto might no longer be part of any deal between Amman and ISIS. But CNN quoted Jordanian Foreign Minister Nasser Judeh as saying that “of course” the Japanese hostage’s release would be part of any exchange.

In the first of three videos purportedly of Goto, released last week, a black-clad masked figure with a knife said Goto and Yukawa would be killed within 72 hours if Japan did not pay ISIS $200 million.

A video on Saturday appeared to show Goto with a picture of a decapitated Yukawa, saying his captors’ demands had switched to the release of al-Rishawi.

Tuesday’s video featured an audio track over a still picture that appeared to show Goto holding a picture of a now bearded Kasaesbeh.

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