BERLIN: The German parliament will approve a symbolic resolution on Thursday that declares the 1915 massacre of Armenians by Ottoman forces a "genocide", a move that risks aggravating tensions with Turkey at a sensitive time for Berlin and its European partners.

Turkey rejects the idea that the killings of up to 1.5 million Christian Armenians during World War One amounted to a genocide and has warned German Chancellor Angela Merkel in the run-up to the Bundestag vote that it will damage bilateral ties.

The timing could not be more awkward for Merkel, who has staked her political future on a deal with Turkey under which Ankara has agreed to stem the flow of refugees to Europe in exchange for cash, visa-free travel rights and accelerated talks on European Union membership.

After repeated delays over the past year, Merkel is powerless to stop the resolution, which has been championed by the opposition Greens party and is also supported by lawmakers from her conservative bloc and the centre-left Social Democrats.

Berlin is expecting a backlash from Ankara. Last year, when neighbouring Austria passed a similar declaration, Turkey recalled its ambassador to Vienna and warned of "permanent negative effects" on relations.

But German officials hope the vote will not undermine the migrant deal between the EU and Turkey, which has been under a cloud since Turkish President Tayyip Erdogan pushed out his prime minister last month and began questioning parts of the agreement.

"We can only hope this doesn't lead to an over-reaction from the Turkish side," said Franz Josef Jung, a senior lawmaker in Merkel's Christian Democratic Union (CDU).

"YES, GENOCIDE"

"Despite some of his rhetoric, we believe Erdogan has a strong interest in making the migrants deal work and will not allow this to get in the way," added a German official close to Merkel who requested anonymity.

Merkel will not be in the Bundestag for the vote due to public appointments, a spokeswoman said.

The resolution uses the word "genocide" in the headline and text. It also acknowledges that the German Empire, then a military ally of the Ottomans, did nothing to stop the killings.

"The fate of the Armenians is exemplary in the history of mass exterminations, ethnic cleansing, deportations and yes, genocide, which marked the 20th century in such a terrible way," the resolution reads.

More than 20 other countries, including France, have passed similar resolutions in past years, infuriating Turkey, which accepts that many Armenians were massacred in 1915 but denies there was any organised campaign to wipe them out.

Over a thousand Turks demonstrated against the resolution on Saturday in front of the Reichstag building in Berlin and some German lawmakers say they have been bombarded with hate mail and insults on social media for supporting the motion.