Trump may close US-Mexico border if migrant 'onslaught' isn't curbed

US President Donald Trump threatened on Thursday to send the military to close its southern border if Mexico fails to stem the "onslaught" of migrants from Central America, in a series of tweets that blamed opposition Democrats.

The attack comes less than three weeks before midterm elections where Trump's Republicans are fighting to retain control of Congress, and as thousands of migrants from impoverished Honduras were marching north through Guatemala toward the United States.

"I am watching the Democrat Party led (because they want Open Borders and existing weak laws) assault on our country by Guatemala, Honduras and El Salvador, whose leaders are doing little to stop this large flow of people, INCLUDING MANY CRIMINALS," Trump said.

"In addition to stopping all payments to these countries, which seem to have almost no control over their population, I must, in the strongest of terms, ask Mexico to stop this onslaught - and if unable to do so I will call up the US Military and CLOSE OUR SOUTHERN BORDER!"

The tweets came as Secretary of State Mike Pompeo prepared to embark on a tour of the region that will see him visit Mexico ahead of its December inauguration of President-elect Andres Manuel Lopez Obrador, as well as Panama.

Trump has made cracking down on illegal immigration a keystone of his presidency, but his animus toward Mexico had cooled in recent times with Obrador's election.

Despite their ideological differences, the pair have so far been able to make progress on several issues, including the signing of an updated transcontinental trade pact, the US-Mexico-Canada Agreement (USMCA).

But, possibly with an eye ahead to the forthcoming polls that will be crucial in determining whether the White House will continue to be able to set the legislative agenda, Trump appeared willing to return to his previous fiery rhetoric.

"The assault on our country at our Southern Border, including the Criminal elements and DRUGS pouring in, is far more important to me, as President, than Trade or the USMCA," he said.