"If we do not follow this through we will see that these countries don't regain more jobs," she said, pointing to efforts that have been made to encourage growth.

Sharp-tongued Steinbrueck has criticized the Merkel government for misleading voters on the costs from another Greek bailout. He also urged her to be honest on how long Germany would have to save the debt-ridden country.

On the Syrian crisis, both candidates ruled out German participation in a military strike against Syria, as a recent poll showed that more than half of German people oppose military action by the western countries in Syria.

Merkel stressed the need to work toward finding a joint response from the United Nations to the alleged chemical weapons attack in Syria, while Steinbrueck said he would "greatly regret it" if the United States strikes without an international mandate.

The opinion poll by market research company Forsa showed last week that support for the CDU and its Bavarian CSU sister party stood unchanged at 41 percent, while the SPD party held at 22 percent.

However, it remains unclear whether Merkel's ruling coalition will survive the election even though her CDU and its Bavarian CSU sister party maintain a double-digit advantage over Steinbrueck's SPD in opinion polls.

The wild card is Merkel's junior ruling partner the Free Democrats (FDP), who stands at the threshold of 5-percent minimum support for entering into the lower house of parliament. Should the FDP fails to garner 5 percent of votes in the election, Merkel may be forced to form a coalition with the SPD.

When it comes to personal popularity, the gap is wider for the two candidates, with an earlier poll for state broadcaster ARD suggesting that Merkel claims a 68-percent approval rating among voters, maintaining her position as the most popular politician in Germany.

Another opinion poll issued this week for public TV station ZDF showed that 60 percent of respondents preferred Merkel as their chancellor, while only 31 would choose Steinbrueck for the job.    

Fifty-nine-year-old Merkel's domestic popularity owes much to sticking to principles in dealing with the eurozone debt crisis, including pressing indebted eurozone members to carry out austerity measures and reforms. Gravity-defying German economic performance during the crisis also helped to boost support for the Merkel administration.

Merkel joined the CDU and won her first parliamentary seat in 1990, and rose to the head of the CDU in 2000.She beat SPD chancellor Gerhard Schroeder in 2005 and became Germany's first female chancellor, chairing a grand coalition with the center-left SPD.

After her second victory in 2009, she was able to form a coalition government with the pro-business Free Democrats. She is considered as the most influential leader in Europe and one of the most powerful leaders in the world.

Steinbrueck, 66, served as finance minister during Merkel's first term as chancellor. He was nominated last year by SPD party leaders as their candidate in German federal elections in September. He was seen as the center left party's best hope to win back the chancellorship, which was held by SPD under Gerhard Schroeder from 1998 to 2005.

Steinbrueck's election campaign got off on the wrong foot as his profitable speaking engagements caused bad publicity. He earned 1.25 million euros ($1.61 million dollars) for speeches at private functions.

He also made gaffes in the early stage of the campaign including saying that he found the chancellor's salary too low and labelling Italian politicians as "clowns".

The leaders of smaller parties that will take part in the elections will have another election debate on Monday.