The forecasts are due to be published on Tuesday.
In July the IMF predicted Europe's largest economy would expand by 1.9 percent this year and by 1.7 percent next year.
Der Spiegel said the IMF would also call on the German government to do more to boost public and private investment as this would help prop up growth in the short term and also bring benefits for the country in the medium term.
Europe's largest economy had a strong start to the year but shrank by 0.2 percent in the second quarter and some economists have warned of the risk that it was in recession between July and September, especially as business and investor sentiment has weakened.
German Finance Minister Wolfgang Schaeuble has said German growth may just miss the 1.8 percent currently forecast by the government this year, according to sources.