US government shutdown: Six ways it could end

President Donald Trump's standoff with Democrats over a border wall has dragged the US into the longest-ever government shutdown. Both sides appear to be dug in, so how might it end?

Mr Trump continues to call the border a national security crisis while Democrats say he is holding America hostage over an exaggerated threat.

As the nation waits for Washington to move forward, here are a few ways the situation could evolve.

The BBC's Anthony Zurcher also chips in with his thoughts and his probability rating.

1. Things get so bad that Trump caves

Airport security staff, who have been working without pay since December, have begun leaving their jobs, according to officials. Terminals in some major airports have begun experiencing delays or are closing as a result.

Food safety has also come into question as agencies struggle to operate. And on Tuesday the White House said it had doubled its estimate of the economic strain caused by the shutdown.

Mr Trump's public opinion is also suffering, according to new polling.

Anthony: There's always the possibility that the president could just throw in the towel. He did it when the heat became intolerable on his family-separation policy last year. He could do it again, if it becomes increasingly unlikely that Democrats are going to make concessions and the extended shutdown starts eating into the robust US economic growth that he frequently touts.

The big question would be whether his base would go along with this. Would they view a three-week shutdown as enough of an effort to fulfil this campaign promise?

Mr Trump would certainly take heat from conservative commentators such as Rush Limbaugh and Ann Coulter, but at some point the price of the shutdown might exceed the pain of backing down.