Japanese officials were working feverishly Thursday to try and free a Japanese hostage held by the Islamic State group.

It came after a new message purportedly from the extremist group, also known as ISIS or ISIL, announced that a Jordanian pilot would be executed “immediately” if a convicted hotel bomber is not delivered to the Turkish border by sunset Thursday, according to a terror-monitoring group.

The threat, released late Wednesday in a video posted on ISIL-affiliated Twitter accounts, came hours after a 24-hour deadline for the prisoner swap passed. It featured a voice speaking English that the Japanese government said was likely that of Japanese hostage Kenji Goto. Goto, a journalist, is being held with Jordanian air force pilot Mu’ath al-Kaseasbeh.

Japan was studying the new message Thursday. USA TODAY could not independently verify the video.

“If Sajida al-Rishawi is not ready for exchange for my life at the Turkish border by Thursday sunset, 29th of January, Mosul time, the Jordanian pilot Muath al-Kaseasbeh will be killed immediately,” the voice said, according to the terror-monitoring group SITE Intelligence.

The video contains Arabic text and the audio message, which the voice says, “I’ve been told to send to you.”

In Tokyo, Japanese government spokesman Yoshihide Suga said Thursday that the government was analyzing the message. He said Japan was doing its utmost to free Goto, working with nations in the region, including Turkey, Jordan and Israel.

“We are trying to confirm (the message), but we think there is a high probability that this is Mr. Goto’s voice,” he said.

The Cabinet met to assess the latest developments, but did not issue any updates.

Efforts to free al-Kaseasbeh and Goto gained urgency after a purported online ultimatum claimed Tuesday that ISIL would kill both hostages within 24 hours if Jordan did not free al-Rishawi.

Earlier Wednesday, Jordan said it was ready to swap al-Rishawi, convicted of a deadly terrorist attack on a hotel, if al-Kasaseabeh “is released unharmed,” Jordan’s state-run news agency, Petra, said.

There was no word on whether Goto would be included in any exchange as the 24-hour deadline to secure his release passed. The new video did not mention Goto’s fate.

Al-Rishawi had been sentenced to death in Jordan for her involvement in a terrorist attack in 2005 that killed 60 people, most of them attending a wedding reception at an Amman hotel. She survived after her suicide vest failed to explode.

An exchange would run counter to Jordan’s hard-line approach — the same as its U.S. ally — of refusing to negotiate with the Islamic extremists. A swap could set a precedent for negotiating with a militant group that previously has not publicly demanded prisoner releases.

Jordanian King Abdullah II faces growing domestic pressure to bring the pilot home. Al-Kaseasbeh’s father said he met on Wednesday with Jordan’s king, who he said assured him that “everything will be fine.”

The pilot’s capture has hardened popular opposition among Jordanians to the air strikes, analysts said

“Public opinion in Jordan is putting huge pressure on the government to negotiate with the Islamic State group,” said Marwan Shehadeh, a scholar with ties to ultra-conservative Islamic groups in Jordan. “If the government doesn’t make a serious effort to release him, the morale of the entire military will deteriorate and the public will lose trust in the political regime.”

Goto was abducted after entering Syria to search for Japanese hostage Haruna Yukawa, 42, founder of a private security firm, who was taken captive in August, according to reports on Japanese television.

In a video released Jan. 20, ISIL demanded a $200 million ransom for the release of Goto and Yukawa within 72 hours. Abe refused to pay a ransom.

A video released Saturday showed a still photo of Goto holding a photo that apparently shows the dead body of Yukawa. In the video, Goto said the militants had changed their ransom demand and wanted the release of al-Rishawi. USA TODAY could not independently verify the videos.

“This heinous terrorist act is totally unforgivable,” Japanese Prime Minister Shinzo Abe said in parliament Thursday.

Contributing: Doug Stanglin and Michael Winter, USA TODAY, Associated Press