BERLIN - The Christian Democratic Union (CDU), Christian Social Union (CSU) and German Social Democrats (SPD) are holding high-level discussion in final preparation for a new "grand coalition" on Thursday.

German Chancellor Angela Merkel, who's also the leader of CDU, is meeting with CSU leader Horst Seehofer, interim SPD leader Olaf Scholz and SPD faction leader Andrea Nahles in Berlin to clarify remaining questions which were left unaddressed by their recent coalition agreement including the exact composition of cabinet posts.

The SPD is scheduled to publish the outcome of an ongoing internal referendum on whether or not to join another "grand coalition" on Sunday.

A majority vote of the 450,000 SPD party members is the final remaining obstacle to the formation of a new federal government in Germany.

Senior SPD members, including ex-party leader Martin Schulz and parliamentary faction leader Nahles have spent weeks campaigning in favor of signing a coalition agreement with the CSU and CDU.

SPD foreign minister Sigmar Gabriel has expressed his confidence that such attempts to persuade critics will ultimately prove successful.

"I am certain that the coalition agreement will receive a majority," Gabriel told press.

The final draft of policy proposals is widely seen to contain significant concessions from the CDU and CSU on labor market policy, pensions and Europe.

Nevertheless, influential factions within the SPD, including its youth organization (Juso), still hope to prevent the party from joining Merkel's fourth cabinet by casting their votes against the "grand coalition" in the membership poll. The referendum will formally close on Friday.

If SPD members do approve the coalition agreement, Merkel could be re-inaugurated as chancellor in the federal parliament (Bundestag) by March 14.

The CDU has already published a list of the six ministers it will nominate for cabinet roles, while CSU is planning to do so on Monday. According to the newspaper "Rhein-Neckar-Zeitung", the SPD will not do so before March 12.