WASHINGTON (AFP) - President Donald Trump said on Monday (April 23) he may make Mexico halting the flow of undocumented migrants into the US a condition for a renegotiated trade deal.

"Mexico, whose laws on immigration are very tough, must stop people from going through Mexico and into the US. We may make this a new condition of our new Nafta Agreement. Our Country cannot accept what is happening! Also, we must get Wall funding fast," he wrote on Twitter.

The social media announcement came more than a week after the US leader said talks to revamp the North American Free Trade Agreement with Mexico and Canada were "coming along great," although he said there was no deadline for a new deal to be completed.

"It could be two weeks, it could be three months, it could be five months, I don't care," he said.

Trump's threats to exit Nafta have unnerved US industry and members of his own Republican party, who say the country has benefited from the pact.

His promise to build a wall along the border with Mexico was a central plank of his election campaign.

Mexican Economy Minister Ildefonso Guajardo said recently the odds of reaching a deal by early May were as high as 80 per cent, while Canada's Foreign Minister Chrystia Freeland has also touted progress in the talks.

The Mexican foreign minister says Mexico decides on its migration policy "in a sovereign manner", such that it is "unacceptable to condition Nafta renegotiation on unrelated actions".