BERLIN (REUTERS) - German Chancellor Angela Merkel, whose conservatives have fallen behind in polls for an election to replace her later this month, took aim on Tuesday (Aug 31) at the Social Democratic candidate for declining to rule out a coalition with the far left.

After 16 years in power, Merkel's conservatives are facing defeat, with a poll this week showing the centre-left SPD with a five-point lead.

A separate snap poll showed that the SPD candidate for chancellor Olaf Scholz beat other candidates in a televised debate on Sunday.

Polls suggest Mr Scholz could have several possible paths to form a coalition. However, when pressed during Sunday's debate, he did not categorically rule out forming a coalition with the far-left Linke party.

Conservatives say this would mean a big lurch away from Germany's centrist mainstream.

"With me as chancellor there would never be a coalition in which the Linke is involved, and whether this (stance) is shared by Olaf Scholz or not remains open," Dr Merkel told a joint news conference with Austrian Chancellor Sebastian Kurz.

"In this context, there is simply a huge difference for the future of Germany between me and him," she added of Mr Scholz.

Dr Merkel, in power since 2005, plans to stand down after the election. Her conservatives' candidate for chancellor Armin Laschet has failed to capture voters' imagination.