By Dave Graham

MEXICO CITY (Reuters) -Mexico's foreign minister, one of the leading contenders to be the country's next leader, said on Tuesday he will resign to focus on winning the presidential nomination of the ruling party for the 2024 election.

Foreign Minister Marcelo Ebrard, a former mayor of Mexico City, wants to succeed President Andres Manuel Lopez Obrador as the standard-bearer of the leftist National Regeneration Movement (MORENA), which now dominates national politics.

However, for months, opinion polls have tended to give his main rival, Mexico City Mayor Claudia Sheinbaum, a slight edge in the race.

"I have resolved to request and present my resignation from the foreign ministry as of Monday, June 12," Ebrard told a press conference in the capital surrounded by cheering supporters.

Mexico's U.N. ambassador Juan Ramon de la Fuente and ambassador to the U.S. Esteban Moctezuma are viewed by many analysts as the likeliest candidates to replace Ebrard as foreign minister.

Known as a savvy political operator and widely viewed as more socially progressive than Lopez Obrador, Ebrard has been a key troubleshooter for the president in managing disputes with the U.S. over immigration, trade and organized crime.

Ebrard reiterated his view that contenders for the MORENA nomination should leave their posts to ensure a fair campaign, and said he was confident the party would reflect his suggestions in a plan due to be drawn up for the party's selection process on Sunday.

Jorge Buendia, head of polling firm Buendia & Marquez, said Ebrard's step was evidently aimed at beefing up his campaign.

"With this move he's looking to get improved media coverage of himself," Buendia said. "If he manages to get the others to resign too, that will help him."

As foreign minister, it is harder for Ebrard to address domestic issues than for Sheinbaum and Interior Minister Adan Augusto Lopez, another leading contender, Buendia said.

An official said the question of when the presidential hopefuls should stand down was discussed during a meeting on Monday evening between Lopez Obrador and party leaders, including Ebrard, Sheinbaum and interior minister Lopez.

A resignation deadline for them of June 19 had been suggested during the talks, but final decisions would be made during the party's board meeting on Sunday, the official said.

During Monday's meeting, Lopez Obrador said he had urged the party to remain united, and pledged not to influence the outcome of the MORENA contest to pick a candidate.

MORENA is due to choose its presidential nominee by a polling process, though details have not been finalized.

Spurred on by Lopez Obrador's personal popularity, MORENA is heavily favored to win the presidential contest.

Mexican presidents can only serve a single six-year term. The next election takes place in June 2024.

MORENA won a resounding victory on Sunday in a governor's race in the State of Mexico, capturing the country's most populous region and tightening its grip on power.

(Reporting by Dave Graham; Editing by Anthony Esposito, Gerry Doyle and Raju Gopalakrishnan)