By Matthias Sobolewski

BERLIN (Reuters) - Germany plans to set aside 5 billion euros ($5.6 billion) in windfall income this year to help cover the cost of looking after asylum seekers in 2016 while sticking to its promise of keeping the budget balanced.

According to a draft supplementary budget obtained by Reuters on Monday, the government plans to park unexpectedly high revenue from taxes and auctioning mobile telephone licenses in a special fund.

The money would then be released next year to the government and 16 federal states to cope with the influx of migrants, which is forecast to reach 800,000 in 2015 alone.

The huge number of people fleeing war and poverty in the Middle East, Asia and Africa has forced the government to take a new look at its budget plans.

Finance Minister Wolfgang Schaeuble has said he is still aiming to maintain a balanced budget next year. But some lawmakers have questioned whether that will be possible given the rising costs associated with the migrant crisis.

A balanced budget should be comfortably achieved this year thanks to a buoyant economy which has boosted tax income.

However, with the prospects for the coming years less certain, the cabinet will consider the supplementary budget on Tuesday under a broader package of measures to cope with the asylum seekers.

Under Germany's budget law, funds unspent at the end of the year should be used to repay debt. Instead, the government wants to hold over the windfall to 2016 in the hope of meeting the costs of the crisis, which range from social housing to looking after unaccompanied minors, without sliding back into a deficit.

Chancellor Angela Merkel announced last week that the government would pay the states 670 euros each month for every asylum seeker they took in.

German public opinion has been divided on the rising numbers of new arrivals, with some warmly welcoming them but others concerned about how they can be integrated.

The government is under heavy pressure to spend more on improving infrastructure but under the supplementary budget this year's windfall income would be directed to the migrant crisis.

(Reporting by Matthias Sobolewski; Writing by David Stamp; Editing by Noah Barkin)