Mexico Economy Minister Ildefonso Guajardo said on Tuesday he doubted a proposed border tax on Mexican imports to the United States, which the White House has said could be used to finance President Donald Trump's border wall, would ever materialize.

Speaking on the sidelines of an event in Mexico City, Guajardo said he had spoken with several Trump's advisors and had not found any uniformity in their backing of the border tax.

“I wouldn't be so certain that it will end up in the proposal,” he told reporters.

Billed as a way to boost U.S. manufacturing and pay for corporate tax cuts, the so-called border adjustment would essentially tax imports but not exports. It is expected to be part of House tax reform legislation that could emerge in March or April.

It is unclear whether the border adjustment proposal has Trump's support.

The White House has floated the idea of imposing a 20 percent tax on goods from Mexico to pay for a wall at the southern U.S. border. However, aides later said the tax was simply one of various measures being considered.

Trump has threatened to scuttle the North American Free Trade Agreement, which also includes Canada, if he cannot recast it to benefit U.S. interests, raising the risk of a major economic shock for Mexico.