MEXICO CITY, July 12 (Reuters) - Mexican President Andres Manuel Lopez Obrador said on Monday he plans to send a constitutional reform to Congress to protect public sector interests over private companies in the electricity market.

The president said last month he was mulling the reform, which follows various initiatives he has launched to strengthen the hand of the state in the electricity market.

Independent power companies have gone to the courts to block his efforts, and Lopez Obrador used this to explain why he believed a more far-reaching reform was necessary.

"I was thinking initially just to reform the law to correct this situation, but I reached the conclusion ... that we need a constitutional reform so that the public interest has priority," he said, speaking at an event in his home state of Tabasco.

Lopez Obrador did not provide details of the reform or say when he would send it to Congress. The new lower house of the legislative body will convene in September.

The law currently gives preference to dispatching the lowest-cost power onto the grid, which often favors private renewable generators over the state-run Comision Federal de Electricidad's use of fuel oil at several of its biggest plants.

Lopez Obrador has worked to roll back the last government's liberalization of the energy market, which sought to increase private investment in the industry and boost competition in sectors that for decades were dominated by state-run monopolies.

He argues that past, corrupt administrations rigged the market in favor of private interests. (Writing by Dave Graham; Editing by Frank Jack Daniel)