Congressional negotiators reached agreement Monday night to prevent a government shutdown and finance construction of new barriers along the U.S.-Mexico border, overcoming a late-stage hang-up over immigration enforcement issues that had threatened to scuttle the talks.

Democrats and Republicans have reached an agreement in principle over border security to fund the US government and avert another partial shutdown.

The agreement contains only a fraction of the money President Donald Trump wants for his promised border wall and does not mention a concrete barrier.

The deal still needs to be approved by Congress and signed by the president.

Speaking later, Mr Trump did not say whether he would back it. "We're building the wall anyway."

The Democrats - who now control the House of Representatives - have refused to approve the $5.7bn for Mr Trump's wall on the border with Mexico, one of his key campaign pledges.

Lawmakers expressed optimism that a bill would be approved by Friday when funding runs out for some federal agencies.

The previous shutdown - the longest in US history - lasted 35 days and cost the country's economy an estimated $11bn 

Details have yet to be released but aides familiar with the negotiations say it includes $1.375bn in funding for 55 miles (88km) of new fencing at the border, a small part of the more than 2,000 miles promised by the president.

The barrier would be built in the Rio Grande Valley, in Texas, using existing designs, such as metal slats, instead of the concrete wall that Mr Trump had demanded.

There was also an agreement to reduce the number of beds in detention centres to 40,250 from the current 49,057, reports say.