Junko Ishido, mother of Kenji Goto, who is a Japanese journalist being held captive by Islamic State militants, holds letters from her supporters as she speaks to reporters at her house in Tokyo January 28, 2015. [Photo/Agencies]

MOTHER'S PLEA

A spokesman at Japanese Prime Minister Shinzo Abe's office said he had no immediate comment on the Jordanian statement.

The hostage-taking presents Abe with his biggest diplomatic crisis since he took power in 2012, and there has been a flurry of unconfirmed reports in Japanese media that a swap deal involving Goto might be in the works.

Goto's mother, speaking shortly after the presumed deadline had passed late on Wednesday, said: "My emotions are all over the place.

"A time limit has been set, and that has made me nervous," Junko Ishido told reporters at her Tokyo home.

She had earlier urged the Japanese government to do its utmost to save his life and reiterated that her son was not an enemy of Islam.

Abe said Tuesday's video was "despicable". He called on Jordan to cooperate in working for Goto's quick release, but promised that Tokyo would not give in to terrorism.

Goto went to Syria in late October. According to friends and business associates, he was attempting to secure the release of Haruna Yukawa, his friend and fellow Japanese citizen who was captured by Islamic State in August.