Jordan demanded proof Thursday from the Islamic State that a captured Jordanian pilot is still alive, as a deadline reportedly set by the militant group for the kingdom to release a convicted terrorist passed without word on the fate of either prisoner.

“We want to see a proof of life, and then we can talk about an exchange,” Jordanian Information Minister Mohammad al-
Momani told a news conference ahead of the Thursday-at-sunset deadline purportedly set by the militants.

He reaffirmed that Jordan is willing to free Sajida al-Rishawi, 44, an Iraqi sentenced to death for her part in a string of 2005 hotel bombings in Amman, in exchange for the release of Lt. Muath al-Kaseasbeh. The 26-year-old Jordanian air force pilot was captured by Islamic State fighters last month when his F-16 went down in Syria.

“The ultimatum has passed,” Momani said later in an interview. “What we have said is that we demand a proof of life, and we have not received that, which increases the level of suspicion from our side.”

The hostage drama also involves a Japanese journalist held by the Islamic State. An audio recording attributed to the journalist, Kenji Goto, contained a threat to kill the Jordanian pilot if Rishawi wasn’t presented at the Turkish border on Thursday.

An image distributed by Jordanian News Agency shows Jordanian pilot Lt. Muath al-Kaseasbeh. (Jordan News Agency / Handout/EPA)

The case has inflamed public opinion in Jordan and increased pressure on the government to bow out of the U.S.-led campaign against the Islamic State. Kaseasbeh was flying over Syria as part of the battle against the Islamic State.

The Islamic State has beheaded a number of captives and has also reportedly released some hostages in exchange for ransom.

Booth reported from Jerusalem.