German Chancellor Angela Merkel faces off her Opposition challenger Peer Steinbrueck on Sunday night in their only TV debate before the September 22 general election as polls have been suggesting Merkel will win a third term.

The 90-minute TV debate in Berlin was aired live on mainstream German channels as a panel of four interviewers set the agenda and questions that covered issues including taxes, Germany's policy in the eurozone debt crisis, as well as the Syria crisis. An estimated audience of 15-20 million tuned in to the debate.

Both Merkel's conservative Christian Democratic Union (CDU) and Steinbrueck's centre-left Social Democrats (SPD) have campaigned mainly on domestic issues that dominated the debate.

Polls suggested that half of German voters watched the TV debate, while one in three said the debate could influence their choice. It is widely seen as Steinbrueck's last-ditch effort to win more hesitating voters as the elections will be held in just three weeks.