Media playback is unsupported on your device Media caption Federal workers queue up for free food

US President Donald Trump says he will make a "major announcement" later on his Mexican border wall, an issue that has partially shut down government.

The shutdown, now in its fifth week, is the longest in US history and has left 800,000 federal workers unpaid.

Correspondents say Mr Trump may offer a concession on so-called Dreamers, who entered the US illegally when young.

Ahead of the speech, rival Democrats quickly described the expected moves as "unacceptable" and a "non-starter".

Mr Trump is demanding $5.7bn (£4.5bn) in funding for the wall and insists it is needed to end a security crisis on the southern border. The Democrats call it a waste of taxpayers' money.

When is the announcement and what could it include?

It will be from the White House on Saturday afternoon, although it has been put back an hour to 16:00 local time (21:00 GMT).

Mr Trump had a brief exchange with reporters on Saturday morning but gave little away, saying: "I think it'll be an important statement."

The BBC's David Willis in Washington says Mr Trump might be poised to offer a concession on the Dreamers, who entered the United States with their parents illegally.

Image copyright EPA Image caption Donald Trump is unlikely to declare a national emergency on the wall - yet

The Dreamers are currently protected from deportation under a programme that allows them to work but not get citizenship. Mr Trump has been trying to rescind the programme.

Sources told US media Mr Trump may extend protection for Dreamers for three years and also extend visas for Temporary Protection Status holders. More than 300,000 people from countries affected by war or disasters are allowed to live and work in the US under TPS, another system Mr Trump opposes.

Mr Trump will continue to demand $5.7bn for the wall, the sources say.

They also say it is unlikely he will declare a national emergency over the wall.

Such a declaration would free up funds, probably from defence department spending, but be hugely controversial and would almost certainly spark legal challenges.

So could this end the shutdown?

Not if a statement by Democratic House Speaker Nancy Pelosi is anything to go by.

Media playback is unsupported on your device Media caption Five questions about Trump's border wall

The statement read: "Unfortunately, initial reports make clear that his proposal is a compilation of several previously rejected initiatives, each of which is unacceptable and in total, do not represent a good faith effort to restore certainty to people's lives."

The Democrats continue to say they will not negotiate until government is reopened.

There is also no end to the personal rancour. On Saturday, Mr Trump said Ms Pelosi was "under total control of the radical left". There are no talks planned either.

The Democrats are themselves working on legislation to spend hundreds of millions of dollars on other border security issues, including hiring more immigration judges.

How is the shutdown affecting unpaid workers?

Some of the 800,000 federal employees who have been going unpaid since 22 December are in increasingly dire straits.

More than 1,500 appeals have been set up by them on crowdfunding site GoFundMe, seeking a financial lifeline to pay rent or feed and clothe their children.

In desperation, the Department of Agriculture, the Internal Revenue Service and the Federal Aviation Administration have just recalled more than 50,000 employees, who must work without pay.