Mony de Swaan, president of Mexican regulator Cofetel, says that later this month the government will introduce new regulations on the wireline and wireless units of America Movil (AM). The move comes after Mexico’s antitrust agency found AM to be dominant in several market segments during 2009 and 2010. The proposed legislation includes plans to reduce interconnection fees and establish rules for leasing lines from competitors. AM says it is challenging the antitrust’s findings in the hope of blocking the implementation of Cofetel’s new rules. Shares in the company fell by 4% in the wake of the news, their biggest single-day drop for 17 months.