Donald Trump often talks about fortifying the wall along the U.S.-Mexico border at the Mexican government's expense. On Tuesday, the Republican presidential front-runner revealed strong-arm tactics he would use.

"It's an easy decision for Mexico," Trump wrote in a two-page memo sent to the Washington Post. "Make a one-time payment of $5-10 billion to ensure that $24 billion continues to flow into their country year after year."

The memo, titled "Compelling Mexico to Pay for the Wall," threatens to stop Mexican immigrants living in the U.S. from sending money transfers -- known as remittances -- to anyone south of the border. Trump's proposal not only goes against an anti-terrorism law described under the Patriot Act, it has the potential to deepen already-strained relations between the neighboring countries.

Trump's Three-Day Plan

On day one, Trump would redefine "financial transactions" to affect money transfer accounts capable of sending remittances and wire transfers, along with money transfer companies, like Western Union. Companies would have to ensure "the alien first provides a document establishing his lawful presence in the United States," otherwise the U.S. government could seize their assets.

Trump expects Mexico's rebuttal on the second day. He believes the plan justified because Mexico receives about $24 billion a year from transfers, the "majority" of which is sent by undocumented immigrants, though he doesn't give a specific percentage. According to Trump, remittances "serve as de facto welfare for poor families."

By the third day, Trump has given Mexico an ultimatum; either contribute to construction of the border wall or face pernicious regulations, like trade tariffs on imports and cancellations of visas and green card.

"Immigration is a privilege, not a right," Trump wrote. "Mexico is totally dependent on the United States as a release valve for its own poverty - our approvals of hundreds of thousands of visas every year is one of our greatest leverage points."

President Obama Wishes Trump "Good Luck"

At its core, the plan is about halting legal immigration, but it may have an adverse effect if Mexican nationals can't remit funds.

President Obama said as much, calling Trump's proposal "half-baked" and an example of something "primarily put forward for political consumption."

"The notion that we're going to track every Western Union bit of money that's being sent to Mexico, good luck with that," Obama said, speaking to reporters at the White House on Tuesday. The president warned such a plan may have devastating effects on the Mexican economy, which benefited from $25 billion in remittances in 2014 and stands to lose roughly two percent of their gross domestic product.

Long-Term Consequences

In repealing visa accreditations, U.S. immigration reform efforts would stall since more people would cross in search of jobs. Some may resort to underground networks and drug smuggling techniques for money transfer.

"Mexico has taken advantage of us in another way as well: gangs, drug traffickers and cartels have freely exploited our open borders and committed vast numbers of crimes inside the United States," Trump concluded, adding that Americans have "borne the extraordinary daily cost of this criminal activity."

The number of immigrants arriving declined since 2008, according to right-leaning think tank the Center for Migration Studies. Nearly 11 million crossed in the last two years, the country's lowest rate since 2003.

The Great Recession and heightened anti-immigration sentiment during 2012 and 2016 presidential election cycles were a contributing factor, but Trump's proposal - along with his call to deport 11 million undocumented individuals living in the U.S. -- may buck the trend.