Mexico City, Mexico - Mexico on Monday criticized a threat by US President Donald Trump's administration to restrict livestock imports over a pest control row, fanning tensions between the major trade partners.

Trump's Agriculture Secretary Brooke Rollins warned in a letter released Saturday that Washington would restrict imports of live cattle unless Mexico acts to help control a screwworm fly outbreak by Wednesday.

She said that Washington was "very concerned" about the countries' joint campaign against the outbreak in southern Mexico.

The US complained that its southern neighbor was restricting US-contracted planes that release sterile screwworm flies to operating six days a week instead of seven.

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It also accused Mexican authorities of imposing "substantial import duties" on aviation parts, equipment, and sterile fly shipments needed for the operations.

Asked about the US complaint at her morning news conference, Mexican President Claudia Sheinbaum said that while some aspects were justified, "others we consider to be excessive."

She said that the Mexican agriculture ministry was in contact with US authorities to explain its efforts to combat the screwworm, whose flesh-eating larvae can kill cattle.

The row comes against a backdrop of increased trade tensions between the neighboring countries as a result of US tariffs.

While Trump this month left Mexico off the list of nations facing his "reciprocal tariffs," its carmakers as well as steel and aluminum exporters still face damaging duties.

Mexico exported just over one million head of cattle to the US last year, according to estimates by both governments.