The chairman of Germany's Social Democrats (SPD), Sigmar Gabriel, has decided to run against conservative Angela Merkel for the chancellorship in September's federal election, the newspaper Bild reported yesterday.

A spokesman for Gabriel said the party was sticking to its planned timetable. "The SPD will decide on its candidate for chancellor on Jan. 29," he said. Senior party members held a closed-door meeting to discuss election strategy on Tuesday, but the question of who will be the party's top candidate will not be discussed officially, Bild reported.

Gabriel, 57, currently serves as Merkel's vice-chancellor and holds the economy brief, and leads the Social Democratic Party (SPD), junior partner in Merkel's right-left coalition government.

Merkel, 62, who remains popular despite criticism of her liberal asylum policy, announced in November that she would stand for a fourth term in a general election expected this September.

Gabriel has long favored to stand against Merkel, but some party members had hoped that Martin Schulz, the former president of the European Parliament, would take on the role. That now looks unlikely, since he is tipped to become foreign minister, replacing Frank-Walter Steinmeier, whom ruling parties have agreed to elect as German president next month.

Although the SPD wants to win enough votes to form a coalition with the Greens and possibly the radical Left party, most analysts think another 'grand coalition' is the most likely outcome with Merkel clinching a fourth term.