Mexicans have spoken out against the border wall proposed by U.S. President Donald Trump, rejecting any local funds to be used to pay for its construction and arguing it will not stop migrants heading north.

President Donald Trump on Wednesday (January 25) ordered construction of a U.S.-Mexican border wall via directive to cover the roughly 2,000-mile (3,200-km) U.S.-Mexico border.

Federal funds are expected to be used to get construction on the wall started. But Trump is insistent that Mexico will eventually pay for construction.

Speaking to media, Mexico Senate President Emilio Gamboa said no Mexican money will be used to pay for the wall.

"I am convinced and I reiterate; Mexico will not pay for the wall in any way. If the United States, and they are within their right, it's a democratic country, wants to build a wall, then let them with their money," he said.

A small group of protesters gathered outside Attorney General headquarters in Mexico City to protest the new U.S. President, including one man who has filed a legal case against Trump over a failed Baja California resort he says he invested in.

The White House argues the Mexico-U.S. wall would stem the flow of drugs, crime and illegal immigration into the United States.

But protester Maria Garcia believes that it will not stop migrants heading north in search of a better life.

"The wall won't do anything. No wall can block hunger. We already have walls and has it stopped migrants arriving? No. This is nothing more than an initiative based on hate and fear that has been built up and which has worked," she said.

An existing fence between the U.S. and Mexico already exists in parts of the border in cities such as Ciudad Juarez across from Texas.

Trump's border wall directive comes with plans to boost deportation forces in the country as well as stop funds going to states which shelter the roughly 11 million undocumented migrants who already live in the United States.