Mexico has not adequately enacted protocols to curb the spread of New World screwworm, a US official says, in a sign of tension between the two countries as they navigate the northward march of the pest.

US Agriculture Secretary Brooke Rollins blamed a recent screwworm detection less than 113 km from the US border on Mexico's failure to curb cattle movements and inadequate monitoring of fly traps meant to reduce the wild population of screwworm flies, which infest and can kill livestock if untreated.

Screwworm has not yet crossed the US border, according to officials, but poses a multibillion-dollar risk to the US beef industry.

The US has kept its border mostly closed to Mexican cattle imports since May.

The outbreak has heightened tensions between the countries ahead of a planned rev

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