President Donald Trump today signed directives to build a wall along the US border with Mexico and crack down on US cities that shield illegal immigrants, proceeding quickly on sweeping and divisive plans to

curb immigration and boost national security.

The Republican president is also expected to take steps in the coming days to limit legal immigration, including executive orders restricting refugees and blocking the issuing of visas to people from several Muslim-majority Middle Eastern and North African countries including Syria, Sudan, Somalia, Iraq, Iran, Libya and Yemen.

Trump signed two executive orders at the Department of Homeland Security, one ordering construction of a wall along the roughly 2,000-mile (3,200-kilometer) US-Mexico border and the other moving to strip federal grant money from "sanctuary" states and cities, often governed by Democrats, that harbor illegal immigrants.

In cities such as San Francisco local officials, often Democrats, refuse to cooperate with federal authorities on actions against illegal immigrants.

"The American people are no longer going to have to be forced to subsidize this disregard for our laws," White House spokesman Sean Spicer said.

In an interview with ABC News on Wednesday, Trump said construction on the wall would start within months, with planning starting immediately, and that Mexico would pay back to the United States "100 percent" of the costs. Mexican officials have said they will not pay for the wall.

During a White House briefing, Spicer referred to the wall as "a large physical barrier on the southern border."

"Building this barrier is more than just a campaign promise, it's a common sense first step to really securing our porous border," Spicer added. "This will stem the flow of drugs, crime, illegal immigration into the United States," he said.

Trump has long said that he will make Mexico pay for the wall.

"We'll be reimbursed at a later date from whatever transaction we make from Mexico," Trump told ABC on Wednesday. "I'm just telling you there will be a payment. It will be in a form, perhaps a complicated form. What I'm doing is good for the United States. It's also going to be good for Mexico. We want to have a very stable, very solid Mexico."

His plans prompted an immediate outcry from immigrant advocates who said Trump was jeopardizing the rights and freedoms of millions of people.

'POLITICAL THEATER'

"The border wall is about political theater at the expense of civil liberties," said Christian Ramirez, director of the Southern Border Communities Coalition immigrant advocacy group.

"It is not national security policy. Border communities are among the safest in the nation and patrolling them with tens of thousands of heavily armed, poorly trained, unaccountable agents puts lives at risks. This will turn these communities into de facto military zones," Ramirez said.

Trump made cracking down on illegal immigration a key element of his presidential campaign, with supporters often chanting "Build the wall," during his rallies.

The cost, nature and extent of the wall remain unclear. Trump last year put the cost at "probably $8 billion," although other estimates are higher, and said the wall would span 1,000 miles (1,600 km) because of the terrain of the border.

Many Democrats have opposed the plan and could try to thwart any legislation to pay for the construction in the US Congress, although Republicans control both the Senate and House of Representatives.

Spicer said Trump's directives would also end the practice known by critics as "catch and release" in which authorities apprehend illegal immigrants on US territory but do not immediately detain or deport them. He said they would create more detention space for illegal immigrants along the southern border to make it easier and cheaper to detain and deport them.

Trump's actions could fundamentally change the American stance on immigration, as well as further testing relations with Mexico.

Many Americans view their country with pride as "a nation of immigrants," and President John Kennedy wrote a book with that title more than half a century ago. But Trump successfully tapped into resentment toward the roughly 11 million illegal immigrants already in the United States and said during the campaign he would deport them all.

Trump, who in announcing his presidential bid in June 2015 accused Mexico of sending rapists and criminals into the United States, has also threatened to slap hefty taxes on companies that produce in Mexico for the US market and to tear up the North American Free Trade Agreement (NAFTA) between the Mexico, Canada and the United States.

Trump and Mexican President Enrique Pena Nieto are due to meet next week.

Asked about Trump's wall, Republican US Senator John McCain said a physical barrier is not enough to secure the border and called for the additional use of observation towers, drones and other technology.

"Walls can be easily breached," McCain, whose home state of Arizona borders Mexico, told MSNBC's "Morning Joe" program.