Donald Trump said he would force Mexico to pay for a border wall with the United States by blocking Mexican immigrants from sending money back home, the Republican presidential front-runner told The Washington Post in a memo.

This marked the first time Trump has disclosed in detail how he would make good on his promise that Mexico would fund the wall he has promised to build if elected president. Mexican leaders past and present have scoffed at the idea that their country would pay for the wall.

In the two-page memo to the Post, Trump said he would take the threat off the table if Mexico made "a one-time payment of $5-10 billion." The transfers would be allowed to continue once the wall is funded, Trump said.

It is uncertain whether the proposal is legally or politically feasible, the Post said.