UPDATE 1-Chile's finance minister resigns in blow to center-left coalition

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SANTIAGO, Aug 31 (Reuters) - Chilean Finance Minister Rodrigo Valdes announced on Thursday that he was resigning, citing differences over economic policy with members of President Michelle Bachelet's center-left coalition government.

Valdes, an economist who has led the finance ministry for the past two years, said some members of the government did not did not share his sense of urgency to promote economic growth in the South American country.

Earlier this week, he criticized a controversial decision by the government to reject a $2.5 billion copper and iron project on environmental grounds, a decision that was backed by Bachelet.

"To advance sustainably toward greater growth requires discipline and the conviction of the government to open spaces so that the private sector can roll out its initiatives with clear rules," Valdes said at a press conference in Santiago.

"But I believe I wasn't able to make everybody share this conviction."

It was not clear who might replace Valdes. Local media also reported on Thursday that Economy Minister Luis Felipe Cespedes and Finance Subsecretary Alejandro Micco were also going to resign.

Valdes' resignation, ahead of the November presidential and parliamentary elections, was seen by some as a blow to the center-left and its presidential candidate Alejandro Guillier, a senator who is most closely tied to Bachelet's coalition.

Bachelet, who is unpopular due to a weak economy and a string of corruption scandals, has faced criticism that her government is poorly organized and lacks unity.

Former Chilean President Sebastian Pinera, a conservative billionaire, currently leads the presidential polls. (Reporting by Gram Slattery; Editing by Paul Simao)