Republican Presidential candidate Donald Trump has said he would cut off cash sent to Mexico to force them to pay for a border wall with the US.

In a memo to the Washington Post, Mr Trump writes that he would change a law to cut off money transfers to Mexico.

“It’s an easy decision for Mexico,” the candidate writes in the memo, describing it as a “one-time payment” of $5-10 billion.

The Republican frontrunner’s promise to build the wall, in a bid to stop illegal immigration, and force Mexico to foot the estimated $8 billion bill is a cornerstone of his increasingly under fire campaign for the presidency.

Long dogged by questions about how he would force the Mexico to pay for a project, the Washington Post said Mr Trump gave them a memo outlining his plans.

In the two-page document, Mr Trump threatened to change a rule under the anti-terrorism Patriot Act that would cut off a portion of the funds sent to Mexico through money transfers, the newspaper reported.

The billions of dollars wired home by Mexicans living overseas each year is one of the most important sources of income for Mexico along with oil and tourism.

The Washington Post said the feasibility of Mr Trump’s plan was unclear both legally and politically, and that the idea could decimate the Mexican economy and set up an unprecedented showdown between the United States and a key diplomatically.

After the wall is funded, Mr Trump wrote, transfer payments could continue “to flow into their country year after year.”

Called “Compelling Mexico to Pay for the Wall,” the memo included other potential intimidation tactics such as increased trade tariffs, cancelling visas, and higher fees for border-crossing cards, the Washington Post said.

Mexican President Enrique Pena Nieto has made clear “there is no scenario” in which his country would pay for a wall. He has compared Mr Trump’s rhetoric to the rise of European dictators Adolf Hitler and Benito Mussolini.

Meanwhile, a Mexican-Canadian construction worker has hung a flag at Vancouver’s Trump Tower in protest, reports the Independent.

Construction worker Diego Reyna made a personal appeal to Mr Trump when he ascended the soon-to-be completed hotel in Vancouver and hung a Mexican flag. He posed for a photograph in front of the banner and posted it on Facebook.

“WHY DID I PUT A MEXICAN FLAG ON THE ROOF TOP OF TRUMP TOWER VANCOUVER,” he wrote.

“Because from the concrete pouring, finishing, drywall, taping, wood forming and general labour, Mexicans were there, building it, doing good work. The comments Trump has made about us did not stop us from doing the high quality work we have always done, in our home country or when we migrate to the US or Canada.”