Indonesia's capital girded for a potential turnout of millions of protesters asking for a bigger increase in minimum wages in the world's fourth-most-populous nation, a test of President Joko Widodo's pro-business image.

The two-day national protest, starting Dec. 10, will involve four trade union groups, said Muhammad Rusdi, a secretary general at the Indonesian Trade Union Confederation (KSPI), on Wednesday. Workers have seven demands, including renegotiating last month's minimum-wage deal and scrapping outsourcing in state-owned companies, he said.

"Jokowi," as the president, who took office in October, is known, has pursued a two-pronged economic strategy of addressing income inequality and boosting Indonesia's appeal for investment. Faster wage gains would erode a competitive advantage against China as manufacturers look for alternative production locations and contribute to inflation as Jokowi boosts fuel costs.