US President Donald Trump said on Tuesday that the United States would build a "human wall" along the border with Mexico if it cannot construct a physical barrier.

"Tremendous numbers of people are coming up through Mexico in the hopes of flooding our Southern Border. We have sent additional military. We will build a Human Wall if necessary. If we had a real Wall, this would be a non-event!," Trump said in a Twitter post.

Trump is expected to highlight the issue of border security as well as his demand for funds to build a wall during his State of the Union address later on Tuesday.

Congress' refusal to fund a border wall resulted in a partial government shutdown that delayed the annual State of the Union address, originally scheduled for January 29, until February 5. 

Trump has threatened to declare a national emergency to address what he calls a crisis over crime caused by immigrant gangs, drug smuggling and human trafficking of would-be migrants.