"I have high hopes that the Social Democrats will find me an adversary before the next election," the 56-year-old conservative Christian Democrat leader, who has been in her job since 2005 and was re-elected in October 2009, told the Sat.1 television channel.
Merkel said she was not concerned that opinion polls placed her behind potential Social Democrat candidates. "When campaigning comes round, I will put myself into it with enthusiasm," she said.
Two polls last month found German elites were disappointed with Merkel and the performance of her centre-right government.
But the chancellor's former rival during the 2009 race expressed confidence that German voters were ready for a change.
In an interview with the Frankfurter Rundschau newspaper, Frank-Walter Steinmeier, who is now parliamentary group leader for the opposition Social Democrats, stirred up speculation on who might emerge as the SPD candidate.
"Two years after parliamentary elections in 2009, it seems there's no question the public finds more interesting than which Social Democrat will become chancellor," he said.
A survey by broadcaster ARD put both Steinmeier and former finance minister Peer Steinbrück ahead of Merkel in the polls.
Steinbrück has been rumored to be a potential chancellor pick for the SPD, but Steinmeier said the decision on who might take the top spot wouldn't be decided until "late 2012 at the earliest."
Despite the CDU's slip in the opinion polls, Horst Seehofer, head of the conservatives' CSU Bavarian sister party, said there was no reason for worry.
"It's natural halfway through the legislative term," he told German daily Mitteldeutsche Zeitung
He also disputed any question that there was dissent within the conservatives' ranks about seeing the chancellor stand for another term. "Ms. Merkel is totally unchallenged," he said. "She has unlimited support from the CSU."