Junko Ishido displayed a mixture of strength and emotion as she spoke, often tearfully, about her son - knowing that he might have just hours to live.

In a prepared statement she said: "The time left is very short. I would like to say to the Japanese government please save Kenji's life."

Kenji Goto is one of two Japanese men threatened with murder by ISIL, unless Japan pays a $200 million ransom. The government in Tokyo believes that the deadline expires at 2:50pm, Japan time, or 5:50am, GMT.

In long, free-ranging answers to journalists' questions at Tokyo's Foreign Correspondents' Club, Ishido filled in some of the background to her son's presence in Syria.

She said she'd spoken to his wife this week, discovering for the first time that she had given birth just two weeks before Goto's departure for the Middle East.

Ishido said she was angry that her son could have abandoned a fragile baby at such a young age. And she apologised for the inconvenience and troubles his actions had caused.

But there was also maternal pride at his motivations. She said he had gone to rescue a friend, displaying the kindness that she'd observed in her son since he was a toddler.

That friend is Haruna Yukawa, a self-styled military consultant, who had met Goto in Syria in April, and was taken captive by ISIL, reportedly in August.

Ishido apologised at times for going off topic - talking about the perils of nuclear energy, about the need work together for this 'beautiful earth'.

But at other moments she was clear. When asked if prime minister Shinzo Abe should pay a ransom as a predecessor had done in 1977, she said, "I hope very dearly that Prime Minister Abe and others think about these previous examples."