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By Marianna Parraga

HOUSTON, June 9 (Reuters) - Energy company IMPSA has progressed in renegotiating a contract to develop and rehabilitate two key hydroelectric projects in Venezuela, which could add up to 672 megawatts of generation capacity starting in the coming months, the firm's president Jorge Salcedo told Reuters.

A contract signed by IMPSA - originally an Argentine state-owned firm, now owned by the U.S.-based Industrial Acquisitions Fund - and Venezuelan utility Corpoelec more than a decade ago has remained unexecuted amid payment issues and U.S. sanctions.

The pact, supported by bank loans including from the Andean Development Corporation, left equipment manufactured by IMPSA stalled in the company's warehouse in Mendoza, Argentina.

Under a U.S. license granted earlier this year, IMPSA is now moving to sign a contract addendum with Corpoelec to export and install the hydraulic turbines and mechanical equipment, which would allow it to inaugurate two units that are part of the hydroelectric project Tocoma and to rehabilitate three separate units of project Macagua, both in Venezuela's southern region.

"We are looking to reach a final agreement for the delivery of these units and on payments, etc. We have an agreement for 90% of the (contract's) technical and financial aspects," Salcedo said in an interview late on Monday.

Since most of the equipment, which was recently inspected by Venezuelan officials, is available, the contract could lead to the much-needed first capacity expansion in years of Venezuela's electric grid, which is currently operating at a deficit, triggering frequent power outages and rationing.

Washington is pushing a $100 billion energy reconstruction plan for Venezuela, but the deep deterioration of the country's grid, which operates at a fraction of capacity, is seen as a major obstacle to progress. The country last week approved a reform of its electricity law in a preliminary vote.