But she also warned against high expectations for the 17 nuclear power plants in Germany, which are currently scheduled to be shut down in 2021. Opinion polls show a majority of Germans opposed to extending the use of nuclear power.
Merkel said security was the highest priority.
She also said she wanted to give any measure to extend nuclear power a strong legal foundation - which is why she wants to find a way to extend nuclear power without needing approval from the upper house, or Bundesrat, where her centre-right coalition has no majority.
"From the point of view of energy experts an extension of more than 10 years is desirable," Merkel told ARD television. "From an expert point of view an [extension] period of 10 to 15 years is reasonable."
On Saturday Economy Minister Rainer Bruederle said German nuclear power plants should continue operating for a further 12 years beyond their scheduled shutdown date of 2021.
Bruederle, who has strongly backed extending nuclear power use beyond 2021, offered the target ahead of the publication of an energy development plan due at the end of September.
Germany has 17 nuclear plants, whose operators are embroiled in a scrap with Merkel's government over a planned nuclear power tax the government hopes will contribute 2.3 billion euros ($2.93 billion) per year to an austerity programme.
The Stuttgarter Zeitung newspaper had reported Merkel and top cabinet members had agreed to extend the use of nuclear power by 10 years.
Merkel denied that at a news conference on Friday, when the government received an experts' report with four different scenarios that will form the basis for a decision about whether to extend the use of nuclear power and by how long.
Under a nuclear phase-out law passed by the former centre-left Social Democrat-Greens government of Gerhard Schroeder, all German nuclear plants are due to shut by 2021.
Merkel wants to extend their lifespans while forcing utilities to hand over more of their profits.
The biggest utilities, E.ON, RWE, Energie Baden-Wuerttemberg and Vattenfall have campaigned strongly against the nuclear fuel tax and pushed for a tax-deductible fixed charge instead.
Nuclear power providers had threatened to cut investments and possibly even shut down plants if the tax was implemented.
(EurActiv with Reuters.)