Japanese authorities are working to co-ordinate efforts with Jordan and other countries to save a hostage held by the extremist Islamic State group.
"We all have one unchanged goal and we will absolutely not give up until the end. And with that faith, we will try our utmost to reach that goal. That's how it is," said Yasuhide Nakayama, a Japanese deputy foreign minister sent to Amman, Jordan, to work on the crisis.
Back in Tokyo, government spokesman Yoshihide Suga told reporters that the government was still analysing a video posted online that purported to show one of the two hostages, Haruna Yukawa, had been killed.
The government has been in crisis mode since an online video appeared on January 20 that said IS had two Japanese hostages and would kill them within 72 hours unless it paid $US200 million ($A254.37 million).
That deadline passed on Friday.
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Asked if the government had concluded the latest video was authentic, Suga said, "We cannot deny that the likelihood is high."
Attention was focused on trying to save Kenji Goto, a 47-year-old journalist who was shown in the video, holding the photo of Yukawa.
The still picture included a recording of a voice claiming to be Goto, saying his captors were no longer demanding ransom but wanted a prisoner exchange.
The contents of the video message, which differed from earlier videos released by IS, could not be verified.
The Japanese public was shocked by the video and news of the likely killing of Yukawa, a 42-year-old adventurer, who was captured in Syria last northern summer.
Goto is thought to have been seized in late October after going there to try to rescue him.
The United Nations Security Council issued a statement that "deplored the apparent murder" of Yukawa, declaring IS "must be defeated and that the intolerance, violence and hatred it espouses must be stamped out".
