The record-breaking Government shutdown in the US is expected to continue for "quite awhile still", as President Donald Trump and the congressional Democrats go head-to-head over the $5.7 billion border wall.

Constitutional law expert Rick Pildes told Tim Dower it doesn't look like either side is willing to back down.

"I think President Trump has made the decision that it's crucial to maintaining support for his presidency among his core supporters, the ones who are most loyal to him, to actually demonstrate that he is able to generate funding for the wall."

"The Democrats have made the decision that they are not going to support any money for what's called a wall."

"There may be some ways to compromise on border security kinds of issues, but the fight is over funding something that will be known as a wall. Right now both sides seem completely confident of their positions, dug in and not facing strong incentives to compromise."

However the Government staff, who aren't being paid during the shutdown, are starting to feel the affects as the shutdown reaches its 23rd day.

"People have started missing their first paycheck. There are lots of people who live paycheck to paycheck. There are people who are required to continue to go to their jobs even though they are not receiving pay, they will typically received pay eventually once the Government is open, including the time they worked during the shutdown."

"It's extremely difficult on the 800,000 employees who are currently not being paid so that will certainly add pressure."

Pildes says if Donald Trump can find another way to fund the wall it would stop the shutdown.

"One way out of this impasse is if the President can legitimately and lawfully find other sources of money and therefore claim victory."

He said another option is for Trump to declare a national emergency which would allow him to re-purpose money.

"Whether the courts would actually uphold the legality of the claim that this is an emergency is a whole separate question."

Meanwhile, a new poll shows more Americans blame President Donald Trump and Republicans in Congress than congressional Democrats for the government shutdown, and most reject the president's assertion that there is an illegal-immigration crisis on the southern border, according to a Washington Post-ABC News poll.

Support for building a wall on the border, which is the principal sticking point in the stalemate between the president and Democrats, has increased over the past year. Today, 42 per cent say they support a wall, up from 34 per cent last January. A slight majority of Americans (54 per cent) oppose the idea, down from 63 per cent a year ago.

The increase in support is sharpest among Republicans, whose backing for Trump's long-standing campaign promise jumped 16 points in the past year, from 71 per cent to 87 per cent. Not only has GOP support increased, it has also hardened. Today, 70 per cent of Republicans say they strongly support the wall, an increase of 12 points since January 2018.

Concerning the allocation of blame, 53 per cent say Trump and the Republicans are mainly at fault, and 29 per cent blame the Democrats in Congress. Thirteen per cent say both sides bear equal responsibility for the shutdown. That is identical to the end of the 16-day shutdown in 2013, when 29 per cent blamed then-President Barack Obama and 53 per cent put the responsibility on congressional Republicans.

A predictable partisan divide shapes the blame game, with 85 per cent of Democrats citing Trump and Republicans as the cause and 68 per cent of Republicans pointing the finger at congressional Democrats. Independents fix the blame squarely on the president and his party rather than on the Democrats, by 53 per cent to 23 per cent. Women blame Trump and Republicans by a margin of 35 points, and men blame the president and the GOP by 13 points.

The deep partisan divide over who bears responsibility for the partial shutdown and over the wall itself is likely to have contributed to the length of the standoff. Neither the president nor Democratic congressional leaders have shown any willingness to compromise. Republicans in Congress continue to show support for Trump's positions.

Last week, the talks broke down during a contentious meeting at the White House at which Trump walked out when told by House Speaker Nancy Pelosi, D-Calif., that she would continue to oppose the wall in border security negotiations, even if the government was reopened. As of this weekend, there is still no clear path ahead to end the shutdown.

At this point, most Americans say they are not feeling the effects of the shutdown. Eighteen per cent say they have been inconvenienced, including 7 per cent who say it has been a major problem.

If the shutdown continues for several months, as the president has threatened, 38 per cent of Americans say they would consider that a crisis, 41 per cent say it would be a serious problem but not a crisis, and 18 per cent say it would not be a serious problem.

Partisan differences also shape the choices ahead. Of the 54 per cent of Americans who oppose the wall, 27 per cent say Democrats should continue to resist Trump's demands for $5.7 billion for a barrier, and 23 per cent say Democrats should compromise with the president.

Of those 42 per cent who support the wall, 24 per cent say Trump should continue to demand the level of funding he has asked for, and 16 per cent say he should strike a deal with the Democrats.

Overall, Democrats appear somewhat more conciliatory than Republicans. The poll finds that 42 per cent of Democrats who oppose the wall say congressional Democrats should refuse to budge even if it extends the shutdown; 37 per cent say they should compromise with Trump. Among Republicans, 58 per cent both support the wall and say Trump should continue to demand funding, compared with 22 per cent who say he should compromise to end the shutdown.

Trump has threatened repeatedly to declare a national emergency to break the stalemate and to order the start of construction of a wall, although on Friday, he retreated from his previously aggressive rhetoric by noting that he is not ready to take such a step now.

The president faces sizable opposition from the public were he to do so. By more than 2-1 (66 per cent to 31 per cent), Americans say they oppose invoking an emergency to build a border wall. The poll finds 51 per cent say they strongly oppose such a declaration. However, two-thirds of Republicans would support the president's decision to use those powers.

In his nationally televised address he delivered from the Oval Office on Tuesday, Trump asserted that there is a humanitarian and security crisis at the border because of illegal immigration. Nearly half of all Americans (47 per cent) say there is a serious problem at the border but decline to call it a crisis. Just under a quarter label the current situation a crisis.

Almost half of all Republicans (49 per cent) say the situation at the border is a crisis, and 43 per cent say it is serious but not a crisis. Among Democrats, just 7 per cent say the situation amounts to a crisis, and 52 per cent say conditions are serious. Roughly one-fifth of independents agree with Trump's characterization, and about half say things are serious but are not a crisis.

The Post-ABC poll was conducted Jan. 8-11 among a random national sample of 788 Americans reached on cellular and landline phones. The overall results have a margin of sampling error of plus or minus 4.5 percentage points.