(Bloomberg) -- Mexican Economy Minister Tatiana Clouthier stepped down Thursday after co-leading talks with the US and Canada to resolve a dispute over the Latin American country’s nationalist energy policies.

Clouthier tried to contain tears when reading her resignation letter during President Andres Manuel Lopez Obrador’s daily press conference, before quipping that the strain of the job including regularly attending the 7 a.m. briefings had worn her out.

“My capacity to contribute to the team is exhausted,” said Clouthier, who ran Lopez Obrador’s presidential campaign ahead of his landslide victory in 2018 and is seen as a centrist member of his cabinet.

Lopez Obrador said he and Clouthier had discussed her possible departure in July and that she left on the best of terms, adding that he plans to name her replacement on Friday. 

The dispute under the North American free trade deal filed by the US and Canada in July argues that Mexico discriminates against foreign companies trying to operate in the country. After 75 days of talks, the US and Mexico agreed to extend consultations this week, putting off the prospect of a dispute resolution panel for the time being. 

Read More: US, Mexico Agree to Extend Talks on Energy Dispute Past Minimum

Clouthier’s departure is “unexpected and unfortunate” for the trade talks, said Veronica Ortiz, a political analyst and former head of the Mexican Council on Foreign Affairs. “It means that more radical elements of the cabinet are prevailing, and this adds more uncertainty to the process.”

Clouthier, together with Foreign Affairs Minister Marcelo Ebrard, was leading a team of top Mexican officials working to resolve the dispute.

Clouthier’s brother Manuel, a former federal lawmaker, said he hadn’t discussed the matter with his sister  but speculated in a tweet that she quit over Lopez Obrador’s push to give the army more influence in domestic security matters. She also leaves days after Mexico announced a pact with companies to waive import tariffs and health inspections in exchange for them bringing down prices of some food items.

Read More: AMLO Lauds Senate for Extending Army Presence in Mexico Streets

(updates with context from paragraph three.)

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