US President Donald Trump said parts of the US Government will stay closed until Democrats meet his demands to fund his long-promised wall at the US-Mexico border.

Key points: A border wall was one of Donald Trump's key promises during the 2016 election campaign

A border wall was one of Donald Trump's key promises during the 2016 election campaign Rows over how to fund the wall has seen 25 per cent of government departments shut down

Rows over how to fund the wall has seen 25 per cent of government departments shut down Mr Trump last week claimed he'd be "proud" to shut down the government, but now is trying to shift blame

In a Christmas Day appearance in the Oval Office, Mr Trump issued a long defence of his desire for a wall, saying it was the only way to deter criminal elements such as stopping drugs and human traffickers from entering the country.

"We can't do it without a barrier. We can't do it without a wall," he said.

In a nod to the political stakes he has been facing, Mr Trump said he wanted the wall by "election time" in 2020.

The promise of a border wall was a central component of Mr Trump's presidential campaign in 2016.

"I can't tell you when the Government's going to be open. I can tell you it's not going to be open until we have a wall or fence, whatever they'd like to call it," Mr Trump said, referring to Democrats who staunchly oppose walling off the border.

"I'll call it whatever they want, but it's all the same thing."

Democrats oppose spending money on a wall, preferring instead to pump the dollars into fencing, technology and other means of controlling access to the border.

Mr Trump argued that Democrats oppose a wall only because he is for one.

The stalemate over how much to spend and how to spend it caused the partial Government shutdown that began following a lapse in funding for departments and agencies that make up about 25 per cent of the Government.

The Government shutdown does not affect essential government agencies such as the FBI, Border Patrol and Medicare.

However, some 800,000 government workers are affected while some services that include parks and museums would be closed during the shutdown.

The shutdown has affected approximately 25 per cent of the US Government. ( REUTERS/Jason Reed )

Many are on the job but must wait until after the shutdown to be paid again.

Mr Trump claimed that many of these workers "have said to me and communicated, 'stay out until you get the funding for the wall'. These federal workers want the wall. The only one that doesn't want the wall are the Democrats".

The US President did not say how he was hearing from federal workers, excluding those he appointed to their jobs or who work with him in the White House.

But many rank-and-file workers have gone to social media with stories of the financial hardship they expect to face because of the shutdown, now in its fourth day.

Chuck Schumer and Nancy Pelosi, the Democratic leaders of the Senate and Congress, said Mr Trump "wanted the shutdown, but he seems not to know how to get himself out it."

Mr Trump had said he'd be "proud" to shut down the government in a fight over the wall.

"It's a disgrace what's happening in our country but, other than that, I wish everybody a very merry Christmas," he said.

AP

