BRUSSELS (Reuters) - The European Commission will launch calls within days for projects to improve EU supply of critical minerals and hopes soon to begin joint EU purchases along the lines of its existing scheme for gas, a senior commissioner said on Wednesday.

The EU Critical Raw Materials Act is designed to guarantee a supply of lithium, copper and other minerals crucial for the EU's green and digital transitions, to enable the bloc to produce its own electric vehicles or wind turbines and to reduce dependence on China. It enters force on May 23.

Commission Vice-President Maros Sefcovic said the EU executive would convene a first meeting of a board with EU members overseeing the act.

"Within the days after that... we would like to launch the first call for strategic projects," Sefcovic said on the sidelines of the EU Raw Materials Summit in Brussels.

Processing, recycling or mining projects deemed strategic should be able to secure permits in 15-27 months, far faster than normal. Sweden's Eurobattery Minerals AB has said it will submit an application for a mine in Finland to be strategic.

Sefcovic said the Commission was beginning to sketch out plans for joint purchases of up to about 30 materials, building on its experience of common purchases of gas. The EU executive would act as a matchmaker between global suppliers and EU purchasers.

Sefcovic said the scheme should be launched "rather sooner than later", recognising that EU members would need to be convinced, which took some time in the case of gas.

The commissioner said the platform used for gas purchases could serve as a blueprint, though recognised buying multiple different critical minerals would be more complex. The system could also be used to get a more precise sense of future demand.

Sefcovic said the Commission was also looking into the possibility of stockpiling certain key minerals, saying inspiration came from the Japanese model for rare earths.

(Reporting by Philip Blenkinsop; Editing by Alexandra Hudson)

By Philip Blenkinsop