UPDATE 1-Mexico's anti-trust watchdog files Supreme Court case against electricity reform

(Adds details from the complaint)

MEXICO CITY, April 22 (Reuters) - Mexico's antitrust authority on Thursday said it had filed a dispute in the Supreme Court against a government reform that aims to increase the state's role in the power sector and which was last month suspended by a judge citing competition fears.

The proposed changes, which have drawn the ire of leading business groups in Mexico and the United States, were fast-tracked through Congress, where President Andres Manuel Lopez Obrador's ruling party and its allies hold a majority.

The Federal Economic Competition Commission (Cofece) said some of the reforms proposed by Lopez Obrador's government prevent competition in the sector. Previously Cofece had urged the Congress to reject the reforms.

"It breaks the rule of open and non-discriminatory access to distribution and transmission networks, which reduces the ability to compete for certain generators and traders," Cofece said in a statement.

The regulator also said the reforms grant undue advantages to national power utility, the Comision Federal de Electricidad (CFE). It also allows CFE to acquire energy through "non-competitive methods", Cofece said.

Cofece's complaint in the Supreme Court is the latest in a series of disputes between the watchdog and the president over his drive to give the state more control over the energy market.

In February, Mexico's Supreme Court upheld a complaint by Cofece that a number of measures taken by Lopez Obrador to help CFE were unconstitutional.

In March a judge ordered a temporary freeze to the legislation passed by Congress, and Lopez Obrador has called on the Supreme Court to settle the matter.

Since taking office on Dec. 2018, Lopez Obrador has prioritized the health of Mexico’s state-owned energy behemoths, oil company Petroleos Mexicanos (Pemex) and CFE.

(Reporting by Adriana Barera; Writing by Drazen Jorgic; Editing by Frank Jack Daniel)