World top cocoa grower Ivory Coast is on track to meet a U.S.-imposed July 1 deadline to certify its cocoa beans as produced free of the worst forms of child labour...U.S. Senator Tom Harkin and Congressman Eliot Engel, who proposed the scheme in 2001, are visiting the West African state to check progress by the Ivorian government and chocolate industry to eradicate slavery and abusive child labour...U.S. legislators could impose a ban on Ivorian or Ghanaian cocoa purchases if monitoring and corrective schemes are not in place...