President Donald Trump said the U.S. has shut down its border with Mexico because it's 'out of control' but he didn't elaborate on the details in his comments on Thursday.

'Actually, two days ago, we closed the border. We actually just closed it. We say nobody is coming in because it was out of control,' he said to reporters after he called U.S. troops to wish them a Happy Thanksgiving.

'It's not that big a deal,' he said.

The president said he signed an order closing the border two days ago.

When reporters asked if they could get a copy of the order, he responded: 'You don't need it.'

President Trump said the U.S. has shut down its border with Mexico because it's 'out of control'

He did not say what he meant by border closing

It's unclear what the president meant by a border closing.

Asked to clarify what he meant, Trump said if 'it gets to a level where we are going to lose control or where people are going to start getting hurt, we will close entry into the country for a period of time until we can get it under control. The whole border. I mean the whole border.'

Asked again to detail what he meant by closing the U.S. Souther border, Trump responded: 'I have already shut it down. I already shut it down for short periods. I shut down parts of the border because it was out of control. With the rioting on the other side in Mexico. And I just said shut it down.'

In his remarks, the president also got in more slams at the Ninth Circuit Court of Appeals, which ruled against his asylum ban for illegal immigrants last week.

‘We are doing really well considering the laws are a disaster. And if we had the right laws, it would be a lot less expensive and we would do it a lot easier, but we don't have the right laws and we have people interpreting the laws and they always give us a bad interpretation. So hopefully we have shown some light on the Ninth Circuit,’ he said.

The president also said the government may shut down this fall if he doesn't get funding for his border wall

Trump also acknowledged his spat with Supreme Court Chief Justice John Roberts

Trump also acknowledged his spat with Supreme Court Chief Justice John Roberts.

‘I know that Chief justice Roberts, John Roberts, has been speaking a little bit about it. And I think - I have a lot of respect for him. I like him and respect him, but I think we have to use some common sense. It's Ninth Circuit, everybody knows it, it's totally out of control. What they're doing, what they're saying, the opinions are very unfair to law enforcement. They're very unfair to our military. And they're very unfair, most importantly, to the people of our country,’ he said.

Trump had launched another attack on the 9th Circuit earlier in the day and dismissed Chief Justice Roberts' strong rebuke one day on from their extraordinary row over judicial independence.

Labeling the 9th Circuit a 'complete and total disaster' that is 'out of control', the president demanded in a tweet judges not be allowed to 'legislate security' in his early morning attack on Thanksgiving.

The new criticism comes one day after the almost unprecedented row between the Supreme Court Chief Justice and the president of the United States following a strong rebuke from Roberts over Trump calling the 9th Circuit 'Obama judges'.

The row began when Trump railed against the Ninth Circuit and its Obama-appointed judge, Jon Tigar, who ruled against him in his attempt to stop illegal immigrants applying for asylum once they cross the border.

'Every case that gets filed in the Ninth Circuit, we get beaten. And then we end up having to go to the Supreme Court, like the travel ban, and we won,' Trump said after the ruling.

Roberts, who is a Republican and was nominated to the Supreme Court by George W. Bush in 2005, weighed in angrily the next day, issuing a rare statement to say that politics played no part in the judicial system.

He said: 'We do not have Obama judges or Trump judges, Bush judges or Clinton judges.

'What we have is an extraordinary group of dedicated judges doing their level best to do equal right to those appearing before them.

'The independent judiciary is something we should all be thankful for.'

Trump hit back on Twitter afterwards, saying: 'Sorry Chief Justice John Roberts, but you do indeed have ‘Obama judges’, and they have a much different point of view than the people who are charged with the safety of our country.'

Trump said he signed an order closing the border but wouldn't make a copy public

Trump has been railing against a band of migrant immigrants making their way to the U.S.

Trump also slammed Democrats like Hillary Clinton and Senate Democratic Leader Chuck Schumer, saying their stance on border security would hurt them politically.

'I think it's bad for them politically. I think the fact that they're weak on the border is very, very bad for them politically. But you know, I have only been a politician for three years so maybe they know better than me,' he said.

He also said there 'certainly could' be a government shut down this fall if he doesn't get the funds for his border wall.

'Could happen over border security,' he said.

His remarks came after it was revealed White House Chief of Staff John Kelly signed an order late Tuesday that allows U.S. troops stationed at the border use lethal force, if necessary, to stop illegal immigrants from crossing into the United States, it was revealed.

Trump said he didn't want the military 'taken advantage of.'

'If they have to, they have to use lethal force. I hope they don't have to, but you're dealing with a minimum of 500 serious criminals. So I'm not going to let the military be taken advantage of. I have no choice,' he noted on Thursday.

Kelly's move, done to combat a caravan of migrants making their way from Central America to the United States, could be illegal.

‘The brave men and women at Customs Border and Protection willingly put themselves in extremely dangerous situations every day to protect Americans and their families. The President’s authorization ensures the Department of Defense can step in to protect those who protect us,’ Deputy White House Press Secretary Hogan Gidley said in a statement.

Kelly’s aggressive stance comes amid reports he and his protégé Homeland Security Secretary Kirstjen Nielsen could be on their way out the door with President Donald Trump said to be particularly angry that Nielsen is not tough enough on illegal immigration.

White House Chief of Staff John Kelly signed an order late Tuesday that allows U.S. troops stationed at the border use lethal force, if necessary

Central American migrants remain in a shelter at the Sports Center Benito Juarez, in Tijuana

A White House official told DailyMail.com the authorization came from the president and Kelly was merely communicating the instructions.

The official also said the military is not doing ‘law enforcement’ but will be there to protect border agents should the situation require it.

‘Law enforcement’ could violate the 1878 Posse Comitatus Act, which restricts the use of the U.S. military as a police force.

The order, set forth in a ‘Cabinet memo,’ will likely be challenged in court.

It comes after the Ninth Circuit Court of Appeals ruling against the administration’s ban on asylum for illegal immigrants, a decision that infuriated President Trump.

Trump did not sign the ‘Cabinet memo’ allowing the use of force, but the president did sign an earlier ‘decision memo’ that included similar recommendations, according to Newsweek.

United States President Donald J. Trump, center left, and First Lady Melania Trump, center right, listen while speaking to Marines with John Kelly, White House chief of staff, left, at Marine Barracks in Washington, D.C., U.S, on Thursday, Nov. 15, 2018

U.S. Customs and Border Protection (CBP) Special Response Team (SRT) officers stand guard

The order allows troops to perform activities Defense Secretary James Mattis deems necessary to protect border agents, such as ‘a show or use of force (including lethal force, where necessary), crowd control, temporary detention. and cursory search,’ according to the Military Times.

Experts say the authorized authority could cross the legal line.

‘They are pushing DoD’s authority right up to the line of what is permitted without violating the restrictions of Posse Comitatus. Active duty personnel can respond in self-defense of border officials but the perfect world does not exist in factual reality in which this subjective concept can be neatly applied to the environment of border enforcement,’ Brad Moss, a Washington, D.C. based attorney specializing in national security, told Newsweek.

There are approximately 5,900 active-duty troops and 2,100 National Guard forces deployed to the U.S.-Mexico border.

In the ‘Cabinet memo’ that he signed, Kelly justified the action by arguing ‘credible evidence and intelligence’ had suggested the migrants ‘may prompt incidents of violence and disorder.’

Mattis told reporters at the Pentagon Wednesday troops would not violate the Posse Comitatus Act.

Retired United States Marine Corps general and White House Chief of Staff John F Kelly visits the Aisne-Marne American Cemetery and Memorial in Belleau, on November 10, 2018 as part of commemorations marking the 100th anniversary of the 11 November 1918 armistice, ending World War 1

The president has done little to tamp down speculation Kelly's days in the White House could be numbered. The order, set forth in a ‘Cabinet memo,’ will likely be challenged in court

‘I now have the authority to do more. Now we’ll see what she asks me’ to do, Mattis said, referring to Nielsen.

Trump has also advocated for greater force from the military, saying at an event earlier this month: ‘Anybody throwing stones, rocks, like they did to Mexico and the Mexican military, Mexican police, where they badly hurt police and soldiers of Mexico, we will consider that a firearm. We’re not going to put up with that. They want to throw rocks at our military, our military fights back. I told them to consider it a rifle.’

Around 3,000 people from the first of the caravans have arrived in Tijuana, Mexico, across the border from San Diego, California. U.S. Customs and Border Protection said Monday that it closed off northbound traffic for several hours at the San Ysidro crossing.

It has also installed movable, wire-topped barriers, apparently to stop a potential mass rush of people.

Trump has been trying to make a virtual wall of U.S. troops and barbed wire to stop the immigrants as he fights with Congress to get his billion dollar border wall built.

Trump has been railing against a migrant caravan making its way from Central America toward the United States.

He made it a huge issue in the midterm elections, particularly as he campaigned for GOP Senate candidates running in states he won in 2016. Republicans were able to knock off four Democratic senators in these red states.