BERLIN, Oct 26 (Reuters) - The German government has slashed its economic growth forecast for this year to 2.6%, but lifted its estimate for next year to 4.1%, two sources told Reuters on condition of anonymity on Tuesday. The revised government forecast for gross domestic product growth compares with an April prediction for the economy to grow by 3.5% in 2021 and by 3.6% in 2022. Economy Minister Peter Altmaier will present the updated growth forecasts during a news conference on Wednesday. A spokesperson for the Economy Ministry declined to comment. (Reporting by Holger Hansen and Christian Kraemer Writing by Michael Nienaber Editing by Riham Alkousaa)