The Pentagon said Monday it has informed the US Congress that it plans to sell 18 Black Hawk helicopters to Mexico for $680 million. Lawmakers have 30 days as of April 17, when they were notified, to raise any objections. Otherwise, the contract will be concluded. The proposed deal -- announced a few days before a visit to Mexico by US defense chief Chuck Hagel -- is for 18 UH-60M Black Hawks with associated equipment, parts, training and logistical support, said the Defense Security Cooperation Agency (DSCA). "This proposed sale will contribute to the foreign policy and national security of the United States by helping to improve the security of a strategic partner," added the agency, which oversees foreign arms sales. "Mexico has been a strong partner in combating organized crime and drug trafficking organizations," it said.