"Too much innocent blood already has been spilled in Iraq," the president said in a video message. "Give the hostages back to their families.

"There is no political aim that justifies the kidnapping or killing of innocent people. No religion allows such behavior," he added.

The video was due to be broadcast in Germany and throughout the Middle East on Wednesday.

Berlin-born Hannelore Krause and her son were seized by armed men who burst into their home in Baghdad on Feb. 6.

Kidnappers demand troops leave Afghanistan

The 61-year-old woman made a tearful plea for help to German Chancellor Angela Merkel in a video posted by her abductors on an Islamist Web site Saturday.

A previously unknown group called the Arrows of Righteousness threatened to kill the pair unless Germany began to withdraw its 3,000 troops from Afghanistan within 10 days.

German government ministers said they would not bow to the kidnappers demands.

Last Friday, the German parliament approved the deployment of six Tornado reconnaissance warplanes to Afghanistan to assist NATO forces in their ground offensive against Islamist Taliban rebels.

Krause is married to an Iraqi professor and has lived in Iraq for more than 20 years.

Three other Germans kidnapped in the past 16 months in Iraq have all been released unharmed amid reports that ransoms were paid.