Germany's Social Democrat Party (SPD), partners in Chancellor Angela Merkel's government, wants to extend a freeze on arms exports to Saudi Arabia beyond March 9, despite pressure by the UK and France not to do so.
The calls come after the October killing of Saudi columnist Jamal Khashoggi.
In an essay for SPD newspaper Vorwaerts, the party's deputy leader in parliament, Rolf Muetzenich, wrote that "the reasons for the imposition of the moratorium have not changed" since their initial implementation.
The concerns about Saudi arms sales are increasingly dividing the coalition ahead of the European elections.
Those on the left of the SPD wish to avoid losses from voters who are hesitant about arms sales.
However, Airbus and Britain's BAE Systems have warned that an ongoing freeze could affect their financial performance. Current estimates state that since the initial arms ban, €1.5 billion in sales have been lost.
UK Foreign Secretary Jeremy Hunt is scheduled to visit Berlin on Wednesday to try to convince the SPD to exempt defence projects from the freeze on arms exports.