President Donald Trump says illegal immigrants the Department of Homeland Security cannot keep in custody will be transported to cities that promote themselves as safe spaces for illegal immigrants.

'Those Illegal Immigrants who can no longer be legally held (Congress must fix the laws and loopholes) will be, subject to Homeland Security, given to Sanctuary Cities and States!' he said in a Monday tweet.

He called on Congress to return to Washington D.C. to 'fix the immigration laws' in another tweet, as he blamed Democrats for his failure to deliver on a key campaign promise to slow the flow of migrants into the United States.

'Congress should come back to D.C. now and FIX THE IMMIGRATION LAWS!' he insisted.

Lawmakers are on a two-week, legislative recess. They're meeting with constituents in their congressional districts.

The President has the power, under Article II, Section 3 of the Constitution, to call a special session of the Congress any time he chooses. Trump's tweet did not appear to be an order but a suggestion.

President Trump called on Congress to return to Washington D.C. to 'fix the immigration laws' as he struggles to full fill his key campaign promise. They are on a standard two-week recess

Trump also claimed that illegal immigrants the Department of Homeland Security can no longer keep in custody will be transported to cities that promote themselves as safe spaces for illegal immigrants

Trump made building a border wall and stemming the tide of illegal immigrants a key promise of his 2016 campaign.

But as his 2020 re-election bid gets closer, his wall remains unfunded by Congress.

He declared a national emergency to get the money but he will not be able to finish the border barrier before the next presidential election.

Even if he does, his administration has admitted that it won't totally solve the immigration problems the president has been raging about. That will take additional legislation from Congress and new Department of Homeland Security regulations.

Trump fired his Homeland Security secretary Kirstjen Nielsen a week ago as he moved to put immigration hardliners in charge of it.

He insisted Monday, at a tax day event, that American immigration laws are 'horrible and foolish' and they allow thugs to claim asylum.

'It's a big con job that's what it is,' he contended. 'And Congress has to get smart. and when I say Congress, I can't blame the Republicans. The Republicans want to do it.'

He noted that it takes 60 votes in the Senate to pass most bills and Democrats currently control the House.

The president predicted in Minnesota, he state he lost in the 2016 election, that immigration would be a winning issue for him.

'We can retake the House,' he said. 'We can retake the House.'

He said last week that the White House was considering alternative ideas - such as dumping illegal immigrants into sanctuary cities - to control where migrants roam after they're mandatory release from government custody.

White House press secretary Sarah Sanders said Sunday that Trump likes an administration plan to send them to sanctuary cities and called it a win 'everybody' as she appeared on Sunday morning news programs.

'The president likes the idea and Democrats have said they want these individuals into their communities so let's see if it works and everybody gets a win out of it,' she said on ABC's 'This Week.'

Trump made building a border wall and stemming the tide of illegal immigrants a key promise of his 2016 campaign. But as his 2020 re-election bid gets closer, his wall remains unfunded by Congress

The president confirmed that he was 'strongly' considering the measure, after the Washington Post reported on a plan to send immigrants in custody to the district of House Speaker Nancy Pelosi.

Trump also made clear he intends to target the immigrants in U.S. custody in the home-states and districts of his political rivals – despite statements by his staff that it was not in the offing.

'California is always saying 'We want more people.' We will give them a lot. We will give them an unlimited supply,' Trump said Friday.

Pelosi's office blasted his idea. 'Using human beings - including little children - as pawns in their warped game to perpetuate fear and demonize immigrants is despicable,' said Pelosi spokeswoman Ashley Etienne said in statement Friday.

Sanders said the White House has explored a number of options to stop illegal immigrants from coming over the U.S.-Mexico border. She added that the sanctuary cities option would not be a top choice.

'We talked about a number of different things over the last two years that we'd love to see happen. Certainly, this wouldn't be our first choice because ideally we wouldn't be dealing with the massive influx of illegal immigrants coming across the border, the crisis that we have both from a national security and humanitarian standpoint,' she told ABC News.

People belonging to a caravan of migrants from Honduras en route to the United States walk across a bridge as they leave Tapachula, Mexico, in April

White House press secretary Sarah Sanders said President Trump likes a plan to dump illegal immigrants in sanctuary cities

President Donald Trump said he if the cities want more people he'll give them more

She said if immigrants were released into sanctuary cities it would be because of the Democrats.

'If Democrats continue to be unwilling to do that, then we're going to look at all of our options and we don't want to put all of the burden on one or two border communities. And Democrats have stated time and time again they support open borders, they support sanctuary cities. So, let's spread out some of that burden and let's put it in some of those other locations if that's what they want to see happen and are refusing to actually help fix the problem,' she said.

SANCTUARY CITIES - WHAT AND WHERE Sanctuary cities - and states - are those which in broad terms protect illegal immigrants from deportation by federal authorities. There is no legal definition and no single set of laws - so agreeing which places are sanctuary cities or states is in itself contentious. But broadly, most sanctuary cities say that their police officers do not ask for immigration status, and do not report it to the federal authorities when they detain, arrest or process suspects. Most will also decline to detain illegal immigrants on requests from Immigration and Customs Enforcement unless they are accused of serious crimes. The degree of seriousness varies from place to place. In New York, even a felony is no guarantee that an immigration detainer will be obeyed. California is the biggest single sanctuary area, with local law enforcement agencies banned by state law from using money, personnel or equipment to help federal immigration authorities act against illegal. While critics might say some places are sanctuary cities, local lawmakers often deny it. In Los Angeles, where cops are banned from stopping people solely on suspicion of being illegal, the mayor has rejected the label, and frequently co-operates with immigration agencies. Cities which identify as sanctuary include: Berkeley, California, since 1971 San Francisco, CA Boulder, Colorado Hartford, Connecticut St Petersburg, Florida Chicago, Illinois Urbana, IL Evanston, IL New Orleans, Louisiana Albany, New York Kalamazoo, Michigan Jersey City, New Jersey Newark, New Jersey New York, New York Portland, Oregon Philadelphia, Pennsylvania Seattle, Washington Cities accused of being sanctuary cities because of laws which limit co-operation with ICE, but which deny it include: Los Angeles, California Atlanta, Georgia Portland, Maine Baltimore, Maryland Boston, Massachusetts Detroit, Michigan Ann Arbor, Michigan Minneapolis, Minnesota Advertisement

Sanders also sought to unravel a situation in which White House staff and the president had been contradicting one another.

'This was raised at a staff level initially and pushed back on. The president wants us to explore again, so that is being done and they're doing a complete and thorough review. But again, the big thing is, if Democrats, including the mayors and members of Congress in these communities want these individuals, they should be helping the president frankly look for solutions to bring them to their communities instead of fighting that president every step of the way,' she said on 'Fox News Sunday.'

Trump said last week in tweets that the idea was indeed under consideration.

'Due to the fact that Democrats are unwilling to change our very dangerous immigration laws, we are indeed, as reported, giving strong considerations to placing Illegal Immigrants in Sanctuary Cities only,' Trump wrote, confirming a story in the Washington Post, an outlet he often attacks as part of the 'fake news.'

'The Radical Left always seems to have an Open Borders, Open Arms policy – so this should make them very happy!' Trump said.

By adding the word 'only,' the president provided a new detail to the plan.

Although the paper had reported top aides pushed the idea with Immigration and Customs Enforcement, it did not say sanctuary cities would be the only location where his administration would ship the illegal immigrants.

He also took a different tack than the White House, which shortly before his tweet downplayed the idea. 'The idea was briefly and informally raised and quickly rejected, according to a White House statement, the Washington Post reported.

A White House statement in the original story said: 'This was a suggestion that was floated and rejected, which ended any further discussion.'

Trump denied a separate claim from two other news outlets that he offered to pardon his acting DHS secretary if he violates U.S. immigration law.

'I never offered Pardons to Homeland Security Officials, never ordered anyone to close our Southern Border (although I have the absolute right to do so, and may if Mexico does not apprehend the illegals coming to our Border), and am not 'frustrated.' It is all Fake & Corrupt News!,' he said in a Saturday tweet.

Sanders also said Sunday that President Trump did not tell the top border agent he would pardon him if he arrested for enforcing policies to stop immigrants.

'We're a country of laws and we have a president who supports that and is not asking anybody to do anything outside of those bounds. In fact, he's asking Congress to step up and give greater legal standing so they can do more to stop this crisis. No one's trying to skirt the law and certainly not being encouraged by the president to do so,' she said on ABC's 'This Week.'

CNN and The New York Times reported last week that the president - during an earlier visit to the border - offered Customs and Border Protection Commissioner Kevin McAleenan a pardon should he be arrested for enforcing any policy to keep out immigrants that ran afoul of the law.

Sanders slammed a source of the story, picking a fight with Trump nemesis CNN.

'I don't know about you, but CNN isn't usually my first stop for a good source, particularly not when it comes to this president. The president is actually the president trying to enforce laws not go around them,' she said.

Sanders said the president has asked border agents to do 'everything they are allowed to do under the law.

'It's the same thing he says publicly day in and day out. It's the same thing he says behind closed doors to staff, is figure out how we stop this crisis, how we fix this problem,' she said on 'Fox News Sunday.'

The president was reported to have told McAleenan he 'would pardon him if he ever went to jail for denying US entry to migrants,' according to the CNN report, which said the comment was paraphrased.

Trump allegedly dangled the offer on his visit to the border town of Calexico, amid a looming staff shakeup at DHS that would leave McAleenan in charge temporarily.

The network sourced the report to two officials briefed on the exchange, and said it was unclear if it was intended as a joke.

Trump met with McAleenan during a border visit, where he railed against immigration and declared the nation 'full' and unable to take any additional people.

'The system is full. Can't take you anymore. Whether it's asylum, whether it's anything you want, it's illegal immigration. We can't take you anymore, Trump said. 'We can't take you. Our country is full. Our area is full. The sector is full. Can't take you anymore, I'm sorry. Can't happen. So turn around. That's the way it is,' he said.

After mentioning the Border Patrol at the event, Trump mentioned backstage conversations, where he expressed a hint of defeatism about the existing laws.

'And I was telling some of the people before: If it's full, there's nothing you can do about it. We have some horrible court decisions that have been made over the years. It's very unfair and that's the way it is.'

'But the system is full. And when it's full, there's nothing you can do. You have to say, 'I'm sorry, we can't take you.' We've been trying to take people, and I have to disagree with it. We've been trying to take people and you can't do it. You can't do it. So we're going to look at that and we're going to look at it very, very strongly,' Trump said.

As the acting head McAleenan does not need Senate confirmation, although he could be required to testify before Congress on budget matters or as his role as head of the Border Patrol. This would give lawmakers an opportunity to ask him about the reported exchange under oath.