After his party's disastrous result in the September 24 election Schultz had ruled out forming another so-called grand coalition with Merkel's Christian Democratic Union and Bavarian-only sister party, the Christian Social Union, like the one that has governed Germany for the last four years.
Speaking at a news conference after a key party executive meeting in Berlin, Martin Schulz sharply criticized Christian Democrats for leaking information to the media, after a crisis summit hosted by President Frank-Walter Steinmeier on Thursday.
Merkel's party stressed however that was it was seeking is a renewal of its alliance with the SPD, to form a "stable government" for Europe's biggest economy.
The SPD, which saw its participation in a Merkel-led coalition government from 2013-17 rewarded with its worst election result in German post-war history, had been strongly opposed to another "grand coalition".
"There was a broad consensus about not closing down any options concerning the formation of a new government", Schulz told reporters.
In a Facebook Live appearance, Schulz mentioned other possible options for the next government, including a minority administration and a coalition that would include the conservatives, the SPD and the Greens. We should talk about each of these options.
German market evacuated after package with nails found
A package found at a Christmas market in the German city of Potsdam has been confirmed as a nail bomb, local police said. Around half an hour later they sent a second message saying their officers had defused the device.
Saying good riddance to a very active 2017 Atlantic hurricane season
The warm ocean waters kept Ophelia fueled as the hurricane traveled farther east than any major hurricane in the Atlantic to date. Gulf and Southeast coasts as well as the Caribbean were spared from at least indirect effects from the onslaught of storms.
Sam Allardyce signs 18-month deal with Everton
Everton have endured a dismal start to the season and are now 17th in the Premier League after just three wins in 13 matches.
The chairman said the SPD's executive committee would discuss various options on Monday, and make a proposal which would be discussed at SPD's party conference from December 7 to 9 in Berlin.
Meantime, she continues to head a caretaker government made up of her conservatives and the Social Democrats.
"We need a different Europe and the initiatives that the French president has suggested should not be given a "no" from Berlin or left unanswered", he said, referring to Macron's ideas of creating a new eurozone finance minister position and giving the 19-member zone its own budget.
A rebellion is already brewing over entering into a new grand coalition, known as "GroKo" in German.
"Germany's European politics must change", Mr Schulz, a former president of the European parliament, told the magazine.