MEXICO CITY, Oct 17 (Reuters) - Mexico's Senate voted to

amend the country's constitution late on Wednesday to give

dispatch preferences to state electricity company CFE, cementing

the national power generator's preferential status above foreign

or private competitors.

The initiative passed the upper chamber of Congress with 86

votes to 39, meeting the requirement of two-thirds support to

change the constitution.

The constitutional reform will require national grid

operator Cenace to prioritize power generated from the CFE's

power plants, even if it is more costly than power supplied by

private producers.

The proposal already passed the lower house of Congress last

week, with support from the leftist ruling Morena party of

President Claudia Sheinbaum.

The constitutional overhaul of dispatch rules will take

effect once it passes a majority of state legislatures, and is

then published in the government's official gazette.

Like her predecessor, former President Andres Manuel Lopez

Obrador, Sheinbaum has sought to give more control of Mexico's

energy market to state-owned power company Comision Federal de

Electricidad (CFE).

Lopez Obrador sought to enact the same change during his

term, but was thwarted by legal challenges.