Donald Trump has issued a desperate plea to his nation to end what he deemed America's "cycle of suffering".
In his first ever nationally televised prime-time address from the Oval Office, the President called for stronger border protection, saying the US had "run out of space" to hold the immigrants crossing the US-Mexico border.
"America proudly welcomes millions of lawful emigrants who enrich our society and contribute to our nation," he said in the impassioned speech. "But all Americans are hurt by uncontrolled, illegal migration."
Trump said illegal migrants strained public resources, drove down jobs and wages, and served as a "pipeline for vast quantities of illegal drugs".
He described it as a "humanitarian crisis … of the heart and soul", noting that 20,000 migrant children were illegally brought into the US last month. "This is the cycle of human suffering that I am determined to end," he said.
The President went on to acknowledge the violence migrants face in the transition to the US, stating: "One in three women are sexually assaulted on the dangerous trek up through Mexico. Women and children are the biggest victims by far of our broken system. This is the tragic reality of illegal immigration on our southern border."
He said his administration had presented Congress with a "detailed proposal" to "secure the border and stop criminal gangs, drug smugglers and human traffickers".
He has also issued an urgent request for humanitarian assistance and medical support.
Mr Trump reiterated that law enforcement professionals had requested $US5.7 billion for a "physical barrier" to stop immigration across the border, claiming the wall would be paid for through a trade deal with Mexico.
The address to the nation came as the US entered its 20th day of a partial government shutdown over the border.
The President blamed the Democrats for the shutdown, saying: "The federal government remains shut down for one reason, and one reason only. Because Democrats will not fund border security.
"Some have suggested a barrier is immoral. But then why do politicians build walls, fences and gates around their homes? They don't do it because they hate the people on the outside — they do it because they love the people on the inside."
Referencing a series of murders at the hands of "illegal aliens", he said: "How much more American blood must we shared before Congress does its job?"
"This is a choice between right and wrong," he went on. "Justice and injustice. This is about whether we fulfil our sacred duty to the American citizens we serve. When I took the oath of office, I swore to protect our country. And that is what I will always do. So help me God. Thank you and goodnight."
The President is now expected to head to the southern border to draw even more attention to the scene he claims needs a radical solution.
Addressing the nation in response, Democratic House Speaker Nancy Pelosi said that "much of what we have heard from President Trump throughout this senseless shutdown has been full of misinformation and even malice."
She said it was "plain wrong" of him to "withhold the pay checks of millions hundreds of thousands of innocent workers". She said there were better ways to secure the borders, including building infrastructure within the ports of entry and hiring personnel to facilitate trade and immigration at the border.
"The fact is, women and children at the border are not a security threat. They are a humanitarian challenge," she said.
Speaking alongside Pelosi, Senator Chuck Schumer urged the President to reopen the government.
"We address you tonight for one reason only: the President of the United States, having failed to get Mexico to pay for his ineffective and unnecessary border war... has shut down the government.
"American government doesn't work that way. We don't govern by temper tantrum. No President should pound the table and demand he gets his way or the government shuts down."
He said the border can be secured without the $US5.7 billion wall, saying: "The symbol of America should be the Statue of Liberty. Not a 30-foot wall.
"So our suggestion is a simple one, Mr President. Reopen the government. We can work to resolve differences over border security. End this shutdown."
The partial government shutdown is starting to be felt among Americans, with 800,000 federal workers — including "anxious and angry" members of the Secret Service — facing the reality that their next scheduled pay cheques won't be issued.
Julie Burr, 49, said she went into "panic mode" after she was placed on unpaid leave from her job as a Transport Department administrative assistant, telling news.com.au she was "seriously considering" selling off her possessions.
Until either Trump or the Democrats budge, the most vulnerable in society are at risk, with food stamps and federal housing about to be affected.
National parks popular with tourists have closed following health and hygiene concerns as rubbish piled up and toilets overflowed without staff. The Department of Agriculture's Animal Care office has closed its hotline for reporting abuse.
Air travel has been affected as security officers and safety inspectors stay off work. Long queues formed at airports over the weekend and the Air Line Pilots Association International warned the shutdown was "adversely affecting the safety, security and efficiency of our national airspace system."
The economy is set to take a battering, with individuals and businesses struggling to function with nine of 15 government departments closed as well as several agencies.
Farmers already struggling cannot receive subsidies as the Agriculture Department's Farm Service Agency is shut. The Milwaukee Journal Sentinel said the shutdown "could wreak havoc on US agriculture, and the rural economy, as farmers wait on subsidy payments, loans and data they need now to make plans for the spring."
Manufacturers also cannot plan as they have no idea how much materials will cost this year because the Commerce Department is not processing requests for exemptions from metal tariffs.
Craft brewers cannot get approval from the Bureau of Alcohol, Tobacco, Firearms and Explosives for new beer labels.
Up to 39,000 federally backed mortgage applications may have been delayed because of reduced agency staffing, according to real estate marketplace Zillow.
Mr Trump said he could relate to the unpaid workers struggling to make ends meet, but the billionaire businessman's claim drew derision from many ordinary Americans.
The President and White House aides have been repeatedly emphasising the idea there is an immigration crisis on the US-Mexico border, and that a border wall is the solution. This is likely to be a major theme of Mr Trump's speech from the Oval Office — one of a president's greatest political weapons.
He will then head to the southern border on Thursday, set to be the 20th day of government shutdown, to draw even more attention to the scene he claims needs a radical solution.
Both sides agree there is a problem at the border.
Homeland Security Secretary Kirstjen Nielsen cited administration figures showing 161,000 family units crossed the border in 2018, a 50 percent increase from the year before. She also said 60,000 unaccompanied children crossed the border last year, a 25 percent increase.
Mr Trump regularly refers to "criminals" and "terrorists" attempting to enter the US from Mexico, but NBC News said border officials found only six immigrants in the first half of fiscal year 2018 whose names were on a government list of known or suspected terrorists.
However, the Washington Post described a "bona fide emergency" as desperate migrants wait weeks and even months for authorities to process their claims.
The closure of immigration courts due to the shutdown has made matters even worse.
Border agents are overwhelmed with arrests along the border exceeding 2000 a day. Many migrants are turning to people smugglers who are depositing rural South American families in remote areas. Humanitarian care is a growing issue.
The argument is over the solution.
All four living former presidents have said they do not support Mr Trump's border wall idea.
Many Republicans are also uncomfortable with the shutdown over border wall funding.
Several dozen GOP politicians in the House of Representatives may cross the room this week to vote for Democratic bills to reopen shuttered parts of the government, according to Politico.
"We need to reopen the government and then have a serious discussion about border security," Democrat and chairwoman of the House Appropriations Committee Nita Lowey told New York Public Radio.
"Isolate the (border wall) issue, take a month to discuss it, but don't hold up all the essential services — like the Agriculture Department, Interior, parks, housing, transportation — all the other parts of the government.
"The President is really causing great hardship to the average person in this country."
A woman in her 50s has been rushed to hospital with significant injuries.