The Biden administration is making asylum restrictions at the US southern border even tougher, as it is increasingly eager to show voters uneasy over immigration that it is taking a hard stance on border security.

The new rules, which toughen restrictions announced in June, bar migrants from being granted asylum when US officials deem that the southern border is overwhelmed.

Under the previous rules, the US could restrict asylum access when the number of migrants trying to enter the country between the official border crossings hit 2,500 per day.

The daily numbers had to average below 1,500 per day for a week in order for the restrictions to be lifted.

But the version rolled out today says the daily numbers will have to be below 1,500 for nearly a month before the restrictions can be lifted.

And the administration is now counting all children towards that number, whereas previously only migrant children from Mexico were counted.

These changes will make it much more difficult to lift the restrictions and allow people entering the country between the official border crossings eventually to apply for asylum in the US.

Immigration advocates already had harshly criticised the restrictions announced in June, saying the administration was slashing away at vital protections for people fleeing persecution.

But the administration has touted its asylum restrictions, saying they have led to serious drops in the number of migrants coming to the southern border.

The new restrictions go into effect on Tuesday.