President Clinton's drugs policy adviser, Barry McCaffrey, has expressed regret that there was inadequate coordination between the United States and Mexico over an investigation into the laundering of drugs money.

US customs and narcotics agents arrested more than one-hundred people, including officials at several of Mexico's leading banks.

The Mexican government, which was not told in advance about the operation, protested to Washington, saying the agents had illegally crossed into Mexico territory to pursue suspects.

Mr McCaffrey said the Mexican authorities should have been informed, but said he only knew of the operation once the it was concluded.