Japan's deputy foreign minister has said negotiations with the Islamic State group threatening to execute a Jordanian pilot and a Japanese journalist have become "deadlocked," local media reported Saturday.

Yasuhide Nakayama, who is leading Tokyo's emergency response team in Amman, told reporters in the Jordanian capital late Friday that there had been no progress in trying to secure the release of Japanese journalist Kenji Goto and airman Maaz al-Kassasbeh.

"It has become deadlocked," he said, according to Japan's public broadcaster NHK. "Staying vigilant, we will continue analysing and examining information as the government is making concerted efforts together."

IS had vowed to kill Kassasbeh by sunset on Thursday unless Amman hands over an Iraqi female jihadist in return for Goto.

Jordan has demanded evidence that the pilot, who crashed in Syria on December 24, is still alive before freeing would-be suicide bomber Sajida al-Rishawi, who is on death row.

Jordan has offered to free Rishawi, who was convicted for her part in triple-hotel bombings in Amman in 2005 that killed 60 people, if IS releases the pilot.

The Jordanian government has been under heavy pressure at home and from Japan -- a major aid donor -- to save Kassasbeh as well as Goto.

While IS threatened Kassasbeh's life, it was not clear from its latest message if the jihadist group was ready to free him as part of an exchange.

IS had set the Thursday sunset deadline for Rishawi to be released at the Turkish border in return for Goto but there was no news of a swap.

Japan, which plays no military part in the fight against IS, was thrust onto the front line last week when a video appeared in which Goto and Haruna Yukawa, a self-described contractor, were seen kneeling in the desert.

A masked, knife-wielding militant said Tokyo had 72 hours to pay a $200 million (175 million-euro) ransom if it wanted to spare their lives.

When that deadline expired, new pictures appeared to show Yukawa had been beheaded, and a voice identifying itself as Goto demanded the release of Rishawi.