The great wall on the U.S.-Mexico border that President Donald Trump promised on the campaign trail took a big step closer to becoming reality Wednesday when he signed two executive orders aimed at curbing illegal immigration.

Trump insisted that his aim was to keep the nation safe and end "one injustice after another" for the families of Americans killed by undocumented immigrants.

"We hear you, we see you and you will never be ignored again," Trump told victims' relatives at a Department of Homeland Security event after he signed the orders. "You children will not have lost their lives for no reason."

The executive actions include redirecting existing Homeland Security money to erect what the administration described as a "very large" wall on the southern border with Mexico, a signature campaign promise. Additional detention facilities would also be built along the border, according to the action.

"And yes, one way or another, as the president has said, Mexico will pay for it," White House Press Secretary Sean Spicer told reporters earlier Wednesday.

The ultimate impact of the executive order on building a wall along border is not clear, because Congress would have to approve any additional appropriations.

Trump is scheduled to meet with Mexican President Enrique Peña Nieto next week in what could prove a tense faceoff as the two leaders discuss coordination, the dismantling of drug cartels and the flow of arms and cash between the two countries.

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"They have to stop it. We have to stop it. We are going to save lives on both sides of the border,"Trump said Wednesday.

Another executive action on immigration policy includes eliminating federal funding to so-called sanctuary cities — a loose term that refers to communities that shield undocumented immigrants from deportation — unless the money is related to law enforcement. The action also directs the hiring of 5,000 new border patrol agents and would triple the number of Immigration and Customs Enforcement agents.

The Trump administration will also regularly publish a list of jurisdictions that "catch and release" undocumented immigrants who have committed crimes and establish an office for the victims of those crimes. The Justice Department is directed to prioritize immigration prosecutions.

Despite Trump's inflammatory rhetoric on the campaign trail, which included calling Mexican immigrants "rapists" and accusing them of "bringing crime," immigration policy experts say it's tough to pin down figures on the numbers of undocumented immigrants who commit crimes.

In a 2015 report, the Migration Policy Institute, a nonpartisan think tank, estimated that "13 percent of the unauthorized immigrants in the U.S would be considered enforcement priorities" under Obama administration executive actions that focused on non-citizens convicted of serious crimes.

A law enforcement source who asked not be identified told NBC News on Wednesday that U.S. Immigration Customs Enforcement has just more than 40,000 people in custody across the nation. Of those, 17,000 are foreign nationals with criminals records, according to the figures, which are for fiscal year 2017.

The source said the number of people being detained is approaching maximum capacity even as the agency tries to find additional space. In fiscal year 2016, ICE removed 240,255 foreign nationals (PDF), a slight increase from the previous fiscal year (2 percent) but a substantial decrease (24 percent) compared to fiscal year 2014.

Even as the executive orders won plaudits from Republicans, many acknowledged that it was simply "symbolic" or, as Sen. David Perdue of Georgia said in a statement, "a good first step towards fixing our immigration system and solving our national security crisis."

Rep. Mike McCaul of Texas, chairman of the House Homeland Security Committee, said in an interview with Bloomberg before Trump signed the orders that Republicans "finally have the political will to do this." But he went on to say that "the term 'wall' is a bit symbolic" and that it simply stands for "securing and getting operational control of that border."

McCaul also acknowledged that whatever form the wall takes, funding it remains an open question.

Democrats were already pledging to fight a number of aspects of the orders — or even to ignore them altogether.

Jim Kenney, the mayor of Philadelphia, a sanctuary city that would be subject to a federal funding cutoff, said the city wouldn't change its policy despite the orders.

"Given that today's EO was simply a directive and did not even make clear if there were any significant funding streams that the Trump administration could cut off to Philadelphia, we have no plans to change our immigration policy at this time," said the statement, which was first reported by The Philadelphia Inquirer.

And the leader of the California state Senate, Kevin de Leon, hint that he go to court to challenge any move to cut off funding to California's sanctuary cities.

Other actions, which could come as early as this week, may include temporarily limiting immigration to refugees and blocking visas for citizens of Middle Eastern and African countries deemed by the Trump administration to be particularly prone to terrorism. Those nations include Syria, Iraq, Iran, Libya, Somalia, Sudan and Yemen.

"Donald Trump is making good on the most shameful and discriminatory promises he made on the campaign trail," the National Iranian American Council, a Washington-based nonprofit organization, said in a statement. "He called for a Muslim ban and is now taking the first steps to implement one. This will not stand. The American people are better than this."