Efforts by Japan and Jordan to secure the release of two of their nationals held captive by Islamic State militants remain "deadlocked" and the situation remains highly unpredictable, Japanese officials said.
Militants had threatened to kill Jordanian pilot Muath al-Kasaesbeh unless a would-be suicide bomber being held on death row in Amman was handed over by sunset on Thursday.
Japanese journalist Kenji Goto was also being held by the militants.
"The situation is deadlocked," Japan's deputy foreign minister, Yasuhide Nakayama, said in Jordon late on Friday according to Japanese public broadcaster NHK.
Foreign Minister Fumio Kishida said in Tokyo on Saturday that the situation was unpredictable and that anything could happen, NHK reported.
"Anything could happen," he said. "We can't predict it at all. While preparing for every situation, I want to make every effort for Mr. Goto's release."
Chief Cabinet Secretary Yoshihide Suga arrived at the Prime Minister Shinzo Abe's office on Saturday afternoon, and the prime minister is on standby to receive regular updates on the situation, NHK said.