Trump says deal possible with Mexico in migration row

US President Donald Trump said Friday that there is a "good chance" that a deal can be reached with Mexico on controlling migrants to avert the imposition of trade tariffs.

But Trump warned that if an agreement cannot be reached in crunch talks between US and Mexican officials in Washington, that the five-percent tariffs will go into place on Monday -- a move which could clobber Mexico's economy.

"If we are able to make the deal with Mexico, & there is a good chance that we will, they will begin purchasing Farm & Agricultural products at very high levels, starting immediately," Trump tweeted.

"If we are unable to make the deal, Mexico will begin paying Tariffs at the 5% level on Monday!," he said.

Trump made the Twitter comments from Air Force One as it was returning from Europe to Washington, where Mexican Foreign Minister Marcelo Ebrard was meeting with US officials at the State Department for the third day to discuss US demands for a crackdown on Central American migrants crossing into the US from Mexico.

White House official Marc Short signalled that they were poised to issue a legal notification Friday for the tariffs to go ahead on Monday.

However, said Short, Vice President Mike Pence's chief of staff, "I think there is the ability, if negotiations continue to go well, that the president can turn that off at some point over the weekend."