The Jordanian government declared its willingness Wednesday to swap a female prisoner who took part in a deadly rampage of hotel bombings in 2005 for a Jordanian pilot held by the Islamic State extremist group.
However, it was unclear whether the proposed deal for the pilot, Lt. Moaz Kasasbeh, would include Kenji Goto, a Japanese journalist also held hostage by Islamic State.
The fates of the Japanese journalist and the Jordanian pilot have become entwined as Islamic State has threatened to execute both men if Jordan does not free the captive militant.
A reported deadline of late Wednesday afternoon passed without definitive word on the status of the two hostages.
According to a purported voice recording of the Japanese hostage that surfaced late Wednesday, the pilot will be executed "immediately" by Islamic State if Amman does not deliver the female militant to the Turkish-Syrian border by sunset Thursday.
The brief audio is identified as the taped voice of Goto, according to the SITE Intelligence Group, which monitors militant Web activity. In the recording, the man said to be the journalist — "I'm Kenji Goto Jogo," he declares — explains that he was told to deliver the message.
The audio was distributed on Islamic State-linked Twitter accounts, SITE said.
Earlier in the day, Mohammad Momani, a government spokesman, confirmed that Jordan was "ready to release the prisoner Sajida al-Rishawi if the Jordanian pilot ... was released completely unharmed."
Musa Abdullat, a Jordanian lawyer with close ties to Islamist groups in the country, said negotiations were progressing.
"Things are moving in a positive direction," he said, contacted by phone in the capital, Amman. "We expect the coming 10 hours to bring some excellent developments."
Rishawi, who sits on Jordan's death row, is an Iraqi militant who participated in coordinated suicide attacks in 2005 on hotels in Amman that left dozens of civilians dead. The operation, reportedly ordered by Abu Musab Zarqawi, the Jordanian head of Al Qaeda in Iraq -- the precursor to Islamic State -- targeted hotels in Amman's more affluent neighborhoods.
Rishawi survived because her explosive belt failed to detonate, authorities said. She was sentenced to death, but the Jordanian government later instituted a moratorium on death penalties that was only overturned in December.
Since her incarceration, Rishawi has become a cause celebre for militant groups. Many have exhorted fellow Muslims to undertake operations to secure her release, which would be seen as a public relations coup for Islamic State, which now controls large stretches of territory in Syria and Iraq.
The families of both hostages have made public appeals urging Islamic State to release the men.
Kasasbeh, the Jordanian pilot, was reported captured in late December after surviving the crash of his F-16 fighter jet in northern Syria. Jordan is part of the U.S.-led coalition that has been bombing Islamic State targets in Syria since September.
Jawdat Kasasbeh, his brother, confirmed that Rishawi had been transferred from her cell in the Jwaideh prison in Amman to a military jail in Zarqa city, 10 miles north of the capital.
"We hope this is a good sign and will lead to Moaz's release," said the brother, speaking from the family home near the southern Jordanian town of Karak.
A video released on Tuesday depicted what appeared to be Goto, the Japanese journalist, holding a picture of the captive pilot. The journalist said he would be executed within 24 hours if the Jordanian government did not hand over the imprisoned militant. The pilot, Goto said, would be killed before him.
"What seems to be so difficult to understand?" asked Goto. "Her for me. A straight exchange."
An earlier video showed Goto with a picture of a beheaded Japanese hostage, Haruna Yukawa, according to SITE. In those images, Goto said Islamic State had abandoned its original demand for a $200-million ransom and now sought the release of Rishawi.
Islamic State supporters on Twitter were jubilant at the prospect of Rishawi's release. Some went so far as to claim she had already reached Islamic State territory, though there was no indication that she had yet been freed.
Bulos is a special correspondent. Staff writer Patrick J. McDonnell in Beirut contributed to this report.