US President Donald Trump has threatened to use military force to completely close the US-Mexico border.
The warning, via a series of tweets on Thursday, comes as a new caravan of more than 3,000 migrants from El Salvador, Honduras and Guatemala heads north.
Mr Trump has already threatened to cut all aid payments to the three countries over illegal immigration.
The group says they are fleeing violence and poverty.
Parliamentary elections in the Afghan province of Kandahar have been delayed by a week after the assassination of a powerful local police chief.
Gen Abdul Raziq was shot dead by a rogue bodyguard on Thursday.
The Taliban claimed the attack, which came after a high-level security meeting. US commander Gen Scott Miller narrowly escaped unhurt.
The local intelligence head was also killed and the governor was critically injured. Three Americans were hurt.
A spokesman for President Ashraf Ghani said that voting in the province would be delayed by a week in line with the wishes of the people.