BERLIN, April 15 (Reuters) - German Economy Minister Peter Altmaier said on Thursday he expected the government to significantly lift its full-year 2021 forecast for gross domestic product growth after leading institutes revised their own estimates. “We’ll not only be able to stop the economic slump this year, we can reverse it and regain our old strength next year,” Altmaier said, adding he would present the government’s updated GDP growth forecast on April 27. In January, the government predicted GDP growth of 3% for 2021, following a drop of 4.9% in the previous year caused by the coronavirus pandemic. The economic institutes now expect gross domestic product to grow by 3.7% this year, down from their previous forecast of 4.7% last autumn. But they raised their GDP estimate for 2022 to 3.9% from 2.7%, expecting household spending to rebound once coronavirus restrictions are lifted again. (Reporting by Michael Nienaber Editing by Caroline Copley)