Updated

Asylum seekers already camping at border crossings worry that how the Trump administration responds to the caravan of some 4,000 Central American migrants and three much smaller ones hundreds of miles behind it could leave them shut out.

President Donald Trump last week threatened to detain asylum seekers in large tents and send as many as 15,000 active-duty soldiers to the border. He's also spoken of closing the border.

That reaction concerns people like 32-year-old Humberto Alvarez Gonzalez, who waits with dozens of others on the southern end of a bridge in Matamoros, Mexico, that leads to South Texas.

The people waiting at the bridge sleep on cots and rely on donated food and clothing.

Alvarez, a Cuban, hopes he can get across the bridge before the caravans arrive.