Biden's former press secretary Jen Psaki reveals huge 'political vulnerability' for the president: 'They knew they would have to do something'

Joe Biden has only been forced into action on migrant border crossings because it now threatens to cost him November's election, his former press secretary has admitted.

On Tuesday the President announced the first executive action aimed at reducing numbers since he came to office, after a Gallup poll found immigration topping voters' concerns for a third month running.

Donald Trump held a 17-point lead over his rival on the issue in a separate poll last month after promising mass deportation of those crossing illegally should he return to office next year.

'Politically, this is one of the biggest vulnerabilities,' Jen Psaki told MSNBC's Morning Joe on Wednesday.

'They knew they would have to do something like an executive order before the election politically as well. And that's what we're seeing play out.'

Biden's move falls short of an executive order but promises to temporarily suspend the entry of non-citizens across the southern border once the average number of detected crossings exceeds 2,500 a day in a seven-day period.

That suspension will not be lifted until the number falls below an average of 1,500 a day for 21 days.

The move has prompted fury from progressive Democrats with Rep Pramila Jayapal (D-Wash) calling it a 'mistake' and Ilhan Omar (D-Minn) branding it a 'betrayal'.

But Psaki, now an MSNBC host herself, said it was inevitable after attempts to push a border control bill through Congress floundered in the face of opposition from Trump.

'It was a deal that was so conservative, and Democrats gave so much, that Republicans were saying 'wow I can't believe we got all of these things'.

'They knew as soon as that deal fell apart that Donald Trump called Mike Johnson and said 'kill the deal', and Mike Johnson said 'Yes sir, I will kill the deal'.

'They knew in that moment they had to do something.'

There were 2.5 million illegal crossings of the southern border detected last year with a record high of 302,000 in December.

Numbers have fallen since then but crossings routinely exceed the level needed to trigger the crackdown with Border authorities recording 3,500 on Monday.

Biden took 94 executive actions to reverse his predecessor's border policies after taking office but has repeatedly warned that any use of his authority to reduce crossings risks being overturned by the courts.

Anger on the left has been compounded by his decision to use the same section 212(f) of the Immigration and Nationality Act for his executive action that Donald Trump used to block refugees from Muslim-majority countries.

The American Civil Liberties Union had already vowed a legal challenge claiming that the move will illegally deprive migrants the right to seek asylum.

'All of these attempts by the prior administration were ruled unlawful by federal courts,' said a spokesman for Human Rights First.

A study by Pew Research in February found a sharp divide between Republican and Democrat supporters over whether the issue of border crossings could be termed a 'crisis' with 70 percent of GOP voters agreeing compared to just 22 per cent of Democrats.

But a Reuters/Ipsos poll last month suggested that 56 percent of all voters want the government to round up and deport most or all migrants who are in the US illegally.

It found that 70 percent of Republicans described the challenges at the southern border as a 'crisis', compared with just 22 percent of Democrats.

'Regardless of who's mad about the details of what's in here and what isn't in here, it's a political vulnerability for the president and his campaign,' Psaki said.