France and Germany "have a joint responsibility to develop all of Europe further," Gabriel told the AFP news agency, naming Macron's plans for "reform of the economic and monetary union" were a top priority.
"We have to grasp the historic opportunity that we have with Macron, a convinced European," Gabriel said in a written statement. "Otherwise one day the EU wil only exist on paper."
An SPD national conference votes on Sunday on whether to continue negotiations to form a coalition government with Merkel's Christian Democrats (CDU).
The vote is expected to be close, with many SPD members criticising leader Martin Schulz for not winning enough in the long-drawn out negotiations.
When Merkel visited Paris on Friday, Macron praised the "blueprint" agreed by the parties' negotiators.
"The chancellor has ambitions for Europe, SPD leaders have shown they have ambitions for Europe, and the coalition outline has them too," he said.
"Our ambition cannot come to fruition alone," he told a joint press conference with Merkel. "It needs to come together with Germany's ambition."
Macron promises post-Brexit trade agreement ... with limits
As Brexit approaches, Macron said that a special trade agreement between Britain and the EU was possible but said it would be "something perhaps between this full access and a trade agreement".
"To get full access to the single market, you need contribution to the budget and you have to accept the freedoms ... and you have to accept the jurisdiction," Macron told the BBC. "As soon as you decide not to join these preconditions, it's not a full access."
With Paris eager to attract banks and finance houses from the City of London in the aftermath of Brexit, Macron stressed that full access for financial services to the single market "is not feasible".
Following Macron's summit with British Prime Minister Theresa May on Thursday, the UK has agreed to take in 260 unaccompanied migrant children whom it had previously rejected after changing the rules of an agreement.
Britain had agreed to take in a total of 480 unaccompanied minors from France and had taken in 220 of them, but then imposed new admission criteria.
The two countries also agreed to work "upstream" to discourage potential migrants in their countries of origin or ones they pass through to reach the EU, British Home Secretary Amber Rudd said.