BRATISLAVA/BRUSSELS (Reuters) - The European Commission will next week propose extending an EU-wide investment-generating scheme by two years to 2020 and increasing its scope to at least 500 billion euros, European officials said.

In its current form the co-financing scheme - focused on infrastructure, energy, research and education - is using 21 billion euros of EU cash and guarantees to attract private investments for 15 times that amount up to 2018.

"The Commission will present an extension of the program to ...trigger investments of a total of at least half a trillion euros by 2020," one official familiar with the project said.

After its first year, the program is slightly ahead of schedule with already 116 billion euros of private investment generated.

In its most ambitious form, the proposal aims to double the investment generated to 630 billion euros if European governments contribute money.

It is to be presented by Commission President Jean-Claude Juncker in his state-of-the-union speech on Sept. 14, officials said.

(Reporting By Francesco Guarascio and Jan Strupczewski; editing by John Stonestreet)