German Chancellor Angela Merkel called for a burqa ban wherever possible on Monday at her conservative Christian Democrats' (CDU) party conference, as the party gears up to back her for a fourth term.

Merkel told the about 1,000 delegates that last year's storming of German borders by about one million refugees would not be repeated, while calling for a ban on the Islamic full-face veil.

"A situation like that of the summer of 2015 can and should not be repeated," Merkel said at the two-day CDU party conference in the western industrial city of Essen. "This was and remains our declared political goal."

She was speaking ahead of the conference vote, which is also expected to return Merkel for the ninth time as CDU chief after she secured 96.7 per cent of the vote when the ballot for party leader was last held two years ago.

However, it was her call for a ban on the burqa that won her hefty applause from delegates.

"The full veil must be banned wherever that is legally possible," she said.

The CDU has already begun drawing up plans for banning the full veil in areas such as courts, police checks and while driving cars.

She told the conference that refugees had found protection in Germany against war, persecution and lack of perspective in their troubled homelands.

But she also told the conference that "not every refugee can stay."

Delegates celebrated the chancellor's about one-and-half hour speech with an 11-minute standing ovation lasting minutes.

The chancellor called on her party to help her fight the election in September 2017, which she said would be like no other in the history of unified Germany, with the CDU facing challenges from both the left and the right.

A poll published last month by public broadcaster ZDF showed 64 per cent of those surveyed supported the chancellor making a bid for another term as head of Europe's biggest economy.

But the size of Tuesday's vote for Merkel will underscore the degree to which her political standing has suffered as a result of the refugee crisis, which has triggered deep divisions in her party's ranks.

In line with Merkel's call to reduce migration, the CDU conference is expected to toughen up the party's stance on refugees, including measures to step up deportations of failed asylum seekers.

The CDU's moves to forge a more hardline approach to refugees at its conference comes in the wake of a string of state election successes by the right-wing populist Alternative for Germany (AfD).

In particular, the AfD has siphoned votes from the CDU after capitalizing on anger in parts of the German electorate over Merkel's liberal refugee policy.

Merkel told the conference that the priority had to be to ensure the stability of the European Union in the face of international uncertainties.

Germany's key European allies such as France, Italy and the Netherlands, are also facing the threat of a surge in support for populist and eurosceptical parties.

Combined with this has been the June vote in Britain to exit the European Union and the shock victory of the New York billionaire Donald Trump in last month's US presidential election.

"In this situation, in which the world appears to be coming apart, to ensure that Europe does not emerge even weaker from the crises than it went," Merkel said.