Sarkozy's visit was the first time that a French president had campaigned in Germany in the run-up to an election. Merkel is scheduled to make a reciprocal trip to Paris at the end of this month, a diplomat said.
"We carry weight when we are united and when we know what to decide," Sarkozy said in Germany's Bild am Sonntag newspaper, adding that his relationship with Merkel was "efficient."
"She knows that she can rely on me like I know I can rely on her," he said.
However, Sarkozy also said his comments were not intended as an endorsement of support for Merkel in her bid to win re-election as chancellor in September. The French president insisted that was "for the Germans to decide."
Turkey too much for the European Union
Locking step on the issue of Turkish EU membership, the two leaders questioned the wisdom of such a move during a meeting of young politicians from the conservative parties of Germany and France.
Chancellor Merkel said it made no sense for the European Union to continuously expand, if the growth leaves the union unable to operate.
At the same meeting, Sarkozy proposed a large joint economic area, saying that a similar concept might work to bind Russia closer to the EU.
Merkel struck a similar note, saying the EU did not want to ignore the East, but needed to remain functional.
Sarkozy also said he supports Germany's bid for a permanent seat on the UN Security Council.
Over a working dinner, the two leaders are also expected to privately discuss the next European summit in June and the Group of Eight summit in Italy in July.