President Trump said Sunday his administration is focused on preventing a caravan of at least 5,000 Central American migrants heading north in Mexico from reaching the US border. He vowed that if the migrants have not been registered as asylum seekers, they would be turned away at the border.

“Full efforts are being made to stop the onslaught of illegal aliens from crossing our Souther (sic) Border. People have to apply for asylum in Mexico first, and if they fail to do that, the U.S. will turn them away. The courts are asking the U.S. to do things that are not doable!” Trump tweeted Sunday.