"She told me this morning that she sided with her parliamentary group," her spokeswoman Christiane Wirtz told journalists, when asked if Merkel signalled her approval of the Armenian "genocide" resolution during a party meeting on Wednesday.
However, the German leader will not be able to attend the vote at the Bundestag due to other official engagements on her schedule, her spokeswoman said.
Merkel's Christian Democrats and junior coalition partner Social Democrats, along with the opposition Greens, had prepared the resolution entitled "Remembrance and commemoration of the genocide of Armenians and other
Christian minorities in 1915 and 1916", which also carries the contentious word throughout the text.
The text would be put to a vote Thursday but in the run-up to the Bundestag move, Turkey issued stark warnings that adopting the resolution would harm ties.
Turkish President Recep Tayyip Erdogan had also telephoned Merkel on Tuesday over the resolution, while Prime Minister Binali Yildirim called the vote "absurd".
But Armenia's President Serge Sarkissian urged German lawmakers to stand firm.
"It would not be fair to not call the genocide of Armenians genocide just because that makes the head of state of another country angry," he told Bild daily in an interview published Wednesday.
"I am sure that Bundestag politicians see it this way too and will not be intimidated," he added.
Turkey and Armenia have long been at loggerheads over the World War I-era massacre.
Armenians say up to 1.5 million of their kin were killed between 1915 and 1917 as the Ottoman Empire was falling apart but modern Turkey rejects the claim.
Ankara argues that 300,000 to 500,000 Armenians and as many Turks died in civil strife when Armenians rose up against their Ottoman rulers.
The vote comes at a particularly awkward time, as Germany and the European Union need Ankara to help stem a migrant influx even as tensions are rising over a string of issues, including human rights.
The issue is also particularly sensitive in Germany, as it has special ties with Ankara not least due to its three-million-strong ethnic Turkish population which settled following a massive "guest worker" programme in the 1960s and 1970s.
More than 20 nations, including France and Russia, have recognised the Armenian genocide.