Germany currently has 3,500 troops in Afghanistan
The Berlin government has extended the mandate of Germany's military mission in Afghanistan for 14 months and agreed to deploy an extra 1,000 troops there.
The decision would keep German troops in Afghanistan until December 2009, boosting their number to 4,500.
The move requires approval by the lower house of parliament, which was due to debate the issue later on Tuesday.
Germany is currently the third biggest contributor to the 47,000 Nato-led force in Afghanistan.
Ahead of the debate in the lower house of parliament, the Bundestag, German Foreign Minister Frank-Walter Steinmeier warned that it was "not very responsible to wave exit dates around".
Chancellor Angela Merkel's governing coalition has a majority in the Bundestag, which is expected to vote on the deployment issue next week.
Germany currently has 3,500 soldiers in Afghanistan, who are stationed in the relatively calm northern regions of the country.