Schulz, who held talks late on Thursday with President Frank-Walter Steinmeier, Merkel and her Bavarian ally Horst Seehofer, denied he had agreed to another grand coalition.
However, SPD party leadership announced that it would give a formal recommendation on how to proceed to its members by Monday.
Firmly denying that an agreement had been reached on opening negotiations on a grand right-left coalition, Schulz said that all options remained on the table.
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".
"Whoever circulates false reports destroys trust", he said.
Commenting on the SDP's possible coalition with the Conservatives, Schulz has stated that it is not "automatic", adding that the party would discuss alternatives at a meeting next week.
"We have a lot of options for building a government".
The SPD will hold a party congress in Berlin on December 7-9, where it is expected to debate its options.
However, several leading Social Democrat politicians have supported a coalition or are backing a minority CDU/CSU government.
"It's now up to the SPD to provide clarity", said CDU manager Klaus Schueler.
"The decisive question is what do we want to implement, what can we implement - for example in the renewal of the European Union", Schulz said.
Germany's Bild newspaper and the news agencies Reuters and DPA reported earlier on Friday that a deal had been reached to pursue the grand coalition option. French President Emmanuel Macron has offered some important ideas: a European finance minister; Eurobonds to finance a new European investment program; more emphasis on innovation; a financial transactions tax to fund increased aid to Africa, where Europe has a strategic interest in long-term development; and tax harmonization more generally, before the USA triggers a global race to the bottom on taxing corporations and the rich.
"A positive response to Emmanuel Macron will be a key demand in any negotiation with the SPD".