BERLIN - Acting German Foreign Minister Sigmar (SPD) will be replaced by the current Justice Minister Heiko Maas (SPD) in the new "grand coalition" government, the magazine "SPIEGEL" reported on Thursday.

Gabriel wrote on Twitter that he had been "informed" that he would not form part of Chancellor Angela Merkel's (CDU) fourth cabinet by the interim and designated party leaders of the German Social Democrats(SPD) Olaf Scholz and Andrea Nahles.

Gabriel's political future has been the subject of widespread speculation in German media after he publicly accused the party leadership of breaking a promise by originally planning to hand his current ministerial post to Martin Schulz in a new federal government.

The widely-publicized internal dispute culminated in the resignation of Schulz from a prospective cabinet role and created a deep rift between Gabriel and Nahles.

While emphasizing that he would retain his elected seat in the German federal parliament (Bundestag), Gabriel wrote on Thursday that "the time has now come to an end in which I assumed political leadership roles for the SPD."

Gabriel held senior positions for the SPD for 18 years, including party leader (2009-2017), minister for economics (2013-2017), minister for the environment (2005-2009) and governor of Lower Saxony (1993-2003). He was repeatedly listed as one of the most popular German politicians in recent opinion polls.

Reflecting on his career on Thursday, Gabriel recalled an "exciting and eventful time which presented me with great opportunities and experiences." Amongst others, he hereby highlighted his diplomatic involvement in the recent release of Turkish-imprisoned German journalist Deniz Yuecel.

Striking a conciliatory tone at the end of his message, the acting foreign minister wished the next federal government lots of success in safeguarding the interests of Germany and Europe. He praised his successor Maas as an "excellent" candidate to take over the German foreign office.

Having finally secured the approval of the SPD membership in a poll, a new "grand coalition" between the Christian Democratic Union (CDU), Christian Social Union (CSU) and SPD is scheduled to be formally inaugurated in the course of this month.