"The Iranian leadership now has a choice: Now is the moment of truth," Scholz said at the Munich Security Conference.
"We have come a long way in the negotiations in Vienna in the last 10 months. All the elements for a conclusion of the negotiations are on the table," Scholz said.
However, he said, if Iran continues to enrich fuel and at the same time suspends monitoring by the International Atomic Energy Agency (IAEA), then that is unacceptable.
Therefore, he said, it had been repeatedly pointed out that it would now soon have to be decided whether a return to the 2015 nuclear agreement was still appropriate.
"We now have the chance to reach an agreement that will lift the sanctions," Scholz said, but also warned: "If we don't manage to do this very quickly, the negotiations risk failing."
Germany, France and Britain, together with Russia and China, have been mediating between Iran and the United States for months. The aim is to lift U.S. economic sanctions and, in return, to restrict Iran's nuclear program again. The next few weeks are considered crucial for whether the 2015 agreement can be revived.
During former U.S. President Donald Trump's reign, the U.S. had unilaterally withdrawn from the agreement. As a result, Tehran violated the conditions of the agreement. Among other things, the Islamic Republic enriched uranium to a level that is no longer far from a weapons capability.