The chancellor said old certainties about international cooperation had "come under pressure", alluding to strained US-German relations.

This year, President Donald Trump and the chancellor have clashed on German domestic and foreign policy issues.

Mrs Merkel's new year's speech will be broadcast in full later on Monday.

Over the past year, Chancellor Merkel has been a leading defender of multilateralism, in contrast to Mr Trump's America First foreign policy.

"In our own interest, we must take on more responsibility," the German leader said, warning that global problems like climate change, migration and terrorism cannot be solved alone.

By taking up a temporary seat on the UN Security Council in 2019 and 2020, Germany would push for "global solutions", Ms Merkel said.

The chancellor, who will step down in 2021, pledged to increase the country's spending on humanitarian and development aid, and defence.

Mrs Merkel also addressed Germany's deep political divide, conceding her government had let down citizens, but calling for solidarity and cooperation.

"We will only master the challenges of our times if we stick together and collaborate with others across borders."

This year, Mrs Merkel averted the near collapse of her coalition government over a migration row, rising out of Germany's acceptance of more than one million migrants and refugees in 2015.

After her party's poor results in regional elections this year, Ms Merkel announced she would be stepping down as party chairperson, a position she has held for 18 years.