Republican presidential candidate Donald Trump said he would try to force Mexico to pay for his proposed wall along the US border by blocking remittances from immigrants in the US, a move that could deal a devastating blow to the Mexican economy.

In a two-page memo made public on Tuesday, Trump's campaign said that if elected to the White House in November, he would use a US anti-terrorism law to cut off money transfers to Mexico unless it made a one-time payment of $5bn to $10bn for the wall.

"It's an easy decision for Mexico," his campaign said in the memo, dated March 31.

Trump's pledge to build the wall along the southern US border has been a much-touted highlight of a larger platform targeting illegal immigration in the US. Mexico has flatly rejected paying for the wall. It is unclear how much the wall would cost, and such a project would be rife with legal and political hurdles.

Any move to target payments sent back to Mexico from people living in the US could have a crushing financial effect. Mexico is the leading recipient of US remittances, receiving nearly $25bn in 2014, according to a US General Accountability Office report.

Trump's campaign put the figure at $24bn.

Most of the transfers stem from California, Texas, Illinois and New York, according to a Wall Street Journal report in February citing Bank of Mexico data.

The move could also affect banks and companies that handle wire transfers such as Western Union Co, MoneyGram International Inc and PayPal Holdings Inc, which last year acquired digital money transfer provider Xoom.

Trump, front-runner to be the Republican nominee for the the November 8 election, has angered many on both sides of the border with his comments about Mexico. In addition to the wall, he has also accused Mexico of sending rapists and drug runners to the US. Democrats and many Republicans have repeatedly condemned his comments as inflammatory and unrealistic.

But his remarks have been enthusiastically received by his supporters, especially by white working-class voters.

In the memo, Trump's campaign repeated its pledge to also target visas, either by cancelling them or charging higher fees for Mexicans to visit the US.

"The cost of a border wall is nothing compared to the hundreds of billions we spend year after year providing services and benefits to illegal immigrants," said the memo, first reported by the Washington Post.

In Mexico, President Enrique Pena Nieto and other officials have repeatedly said they will not pay for any wall. Last month, some Mexicans turned to burning effigies of Trump in protest.

Representatives for the Mexican government did not immediately respond to a request for comment.

The memo on paying for the wall emerged as Republican candidate Ted Cruz appeared set to beat Trump in Wisconsin's primary contest on Tuesday, a win he would hope would mark him as the best alternative to the New York billionaire.