(Adds details on exports, sales forecast)
MEXICO CITY, Aug 6 (Reuters) - Mexico's auto production slid 2 percent and exports fell 2.3 percent in July compared to the same month a year earlier, the Mexican Auto Industry Association (AMIA) said on Thursday, marking their first declines this year.
Mexico produced 254,312 vehicles and exported 226,511 autos in July, AMIA said.
Exports to the United States, which represent about 70 percent of Mexico's auto exports, fell 9.1 percent in July, compared to the same month a year ago.
AMIA President Eduardo Solis said at a news conference that he did not know why the production and exports numbers dropped last month, but added that he did not think it represented a trend.
Accumulated exports and production both rose in the first seven months of the year, compared to the same period a year earlier, AMIA reported.
The auto sector makes up about 30 percent of Mexico's exports, according to the national statistics institute.
The Mexican Association of Automobile Distributors (AMDA) also said on Thursday that it had revised its domestic sales forecast for the year up to 1,331,312 vehicles, from a previous prediction of 1,287,000 autos.
Domestic auto sales jumped 16.1 percent in July, compared to the same month last year. (Reporting Joanna Zuckerman Bernstein; Editing by Meredith Mazzilli)