MEXICO CITY - Mexican President Andres Manuel Lopez Obrador on Friday said he would seek to change mining law to secure the country's lithium for the nation if his constitutional reform to boost state control of the power market fails to pass Congress next week.

The president had earmarked lithium as part of his electricity reform, but the opposition has said it will not support the legislation, meaning the government looks likely to fall short of the two-thirds majority required for approval.

Lopez Obrador was speaking as he hailed a Supreme Court ruling on Thursday that narrowly upheld a key part of a separate law promulgated last year which bolsters state control of the electricity market at the expense of private companies.

A two-thirds majority in the court was needed to declare the legislation unconstitutional, and a key portion of it giving priority to state power utility Comision Federal de Electricidad on when plants come online survived by just one vote.

Some legal experts said that meant that challenges against the legislation could still prosper. Critics of the legislation said Lopez Obrador had therefore won a pyrrhic victory at best.

Because a majority of the judges ruled against key parts of the bill, tribunals that require only a simple majority will likely base rulings on future challenges on that precedent, said Derek Woodhouse at global law firm CMS.

Still, Lopez Obrador said Thursday's ruling had been a "good day for the nation" and again sought to pressure opposition lawmakers into supporting his constitutional reform by suggesting that those who did not would be "traitors."

But in an acknowledgement that defeat was possible, he said he was preparing to send another initiative to Congress to change mining law to secure control of lithium deposits if lawmakers failed to pass the constitutional change.

He denied media reports that the government had leant on the court justices to secure enough votes before going on to praise one of the judges who backed his legislation.