Spiegel reported on Tuesday that the document would include punishments for “travelling or seeking to travel, if the trip is carried out to commit, plan or prepare terrorist acts”.
Government sources told the magazine that the cabinet was likely to agree on the new text on Wednesday without change, sending it on to the Bundestag (German parliament) for approval.
“Above all we're doing something that will make Germany more secure,” Justice Minister Heiko Maas said.
A 2014 UN resolution obliges countries to punish “foreign fighters” travelling to conflict zones in Iraq and Syria.
Until now, German law has only contained punishments for people who travel abroad to train for armed combat as a member of a recognized terrorist organization.
But there are believed to be around 600 Islamists from Germany who have simply travelled to the battle zone and taken up arms independently, falling outside existing laws.
Maas also announced that there would be measures against terrorist financing.
The aim of the new law is both to reduce the numbers of German citizens or residents travelling abroad to fight and to limit the number of extremists returning to Germany.
Justice Ministry sources believe that experienced fighters returning and passing on their knowledge to radicals within Germany pose a “grave threat for internal security”.
Security sources unconvinced
People involved in the fight against terrorism in Germany were unconvinced that the new laws would do much to help.
The new law amounted to “legal gymnastics for the gallery”, head of the Federation of German Detectives in the Bundeskriminalamt (CID) Andy Neumann told Spiegel.
He argued that more qualified investigators and resources were needed to fight the problem, as well as a law allowing so-called “data preservation” - the government or telecom companies keeping copies of all internet communications.
And he said that the law against terrorist financing was useless as long as it required the person giving the money to know that it would be used for criminal acts.
“That's an insurmountable hurdle for any investigator who works on terrorist financing,” Neumann said.
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