Mrs Merkel made her pledge to avert a rebellion by members of her own governing party, some of whom have expressed concern about the one million migrants who will have arrived in Germany by the end of the year.
Her use of the phrase “noticeably reduce” was not accidential. It had been included in a resolution drawn up by the leadership of her party, the Christian Democrats.
This said: “A continuation of the current influx would in the long term overwhelm the state and society, even in a country like Germany.”
The Christian Democrats have seen their support in the polls fall since Mrs Merkel opened Germany’s doors to Syrian refugees.
But speaking to party delegates, she described her existing policy to offer asylum to those fleeing conflict in the Middle East as a “humanitarian imperative”.
‘Germany should be exciting’
She added: “Germany should be a country that is open, curious, tolerant, and even exciting.”
Mrs Merkel defended the “we can do this” catchphrase she used at the height of the refugee crisis, saying her party must show its Christian roots. She received an eight-minute standing ovation at the end of her speech in Karlsruhe.
Despite being named person of the year by both Time magazine and the Financial Times for her response to the crisis, Mrs Merkel has faced criticism for encouraging an influx of migrants and refugees to the EU.
In recent weeks, some migrants who had made it to the Greece/Macedonia border were told they could not travel further north because they were not from countries affected by war.
A build-up of people at a camp on the border came to an end when they were bussed to Athens, but now the Greeks are struggling to cope with the numbers.