* Commission unveiled investment fund last month
* Aim is to revive flagging growth in 28-nation bloc
* Questions remain over fund's impact on budget rules
By Jan Strupczewski
BRUSSELS, Dec 17 (Reuters) - European Union leaders will agree on Thursday to set up a highly leveraged investment fund they hope can kick-start the bloc's economy and reduce high unemployment and public debt.
The plan, presented by the executive European Commission last month and set to be endorsed by the 28 national leaders at a Brussels summit, is to use 21 billion euros of EU funds to attract 15 times more private investment in infrastructure, energy projects, research and education.
"The European Council calls for setting up a European Fund for Strategic Investments (EFSI) with the aim to mobilise 315 billion euro in new investments between 2015 and 2017," read draft conclusions of the summit seen by Reuters.
"The Commission will present a proposal in January 2015, which the Union legislators are invited to agree on by June, so that the new investments can be activated as early as mid-2015."
The plan could be bigger if national governments decide to contribute to the capital of the fund.
Several countries, including Germany and Poland, have signalled they are ready to do so but need clarification on how contributions will be accounted for under EU budget rules.
If buying shares in the EFSI increased their budget deficit and thereby broke EU law, governments would not want to take part, so they are seeking a commitment from the Commission that their fiscal standing would not be affected.
There has been no such declaration so far and the draft conclusions only repeat the position of the Commission, guardian of EU law, which governments say is insufficiently clear.
"The Commission has indicated its intention to take a favourable position towards such capital contributions in the context of the assessment of public finances under the Stability and Growth Pact," the draft conclusions said.
Italian Prime Minister Matteo Renzi has called for investment spending to be excluded from deficit accounting, but such decisions are unlikely at the summit as they would mean budget rule changes that Germany especially does not favour.
EU officials said the Commission was more likely to explain how it would treat such investment in a report on "flexibility" in budget rules due in January.
Governments also want to clarify who would choose which projects the EFSI backs. Some countries say the fund should finance projects on their territory if they buy EFSI shares, but others want decisions to be taken by the European Investment Bank to ensure the most economically viable plans get money. (Additional reporting by Francesco Guarascio; Editing by Alastair Macdonald and Gareth Jones)