Parts of the US government have shut down after Congress failed to reach agreement on a spending deal.
Republicans in the Senate haven't secured the votes needed to approve 5-billion dollars demanded by Donald Trump for a border wall with Mexico.
Funding to build it has been staunchly opposed by Democrats.
President Trump insists it's needed, saying in a video posted on Twitter: "Our great coyuntry must have border security.
"We don't want people coming in that aren't supposed to be here.
"We want people coming in through a legal process".
OUR GREAT COUNTRY MUST HAVE BORDER SECURITY! pic.twitter.com/ZGcYygMf3a
— Donald J. Trump (@realDonaldTrump) December 22, 2018
Democrats will take control of the House in January, and they oppose major funding for construction of any wall along the border with Mexico.
Senate Democratic leader Chuck Schumer told the Senate: "President Trump has thrown a temper tantrum and now has us careening towards a 'Trump shutdown' over Christmas.
"You're not getting the wall today, next week or on 3 January, when Democrats take control of the House."
A partial government shutdown would see staff at affected agencies limited to those deemed "essential" to public safety.
Those workers would not get paid until the dispute was resolved.