The White House said today that US President Donald Trump will announce the "national emergency" to complete the financing of the wall he wants to build on the border with Mexico to combat illegal immigration.

"The president will sign the federal government financing law and, as he has already said, he will act under decrees - especially in the case of national emergency - to end the national and humanitarian security crisis on the border," said administration spokeswoman Sarah Sanders.

"Once again, the president sticks to his promise to build the wall, protect the borders and ensure the security of our great country."

Just before the White House announcement, US Senate Majority Leader Mitch McConnell said President Trump would announce the state of "national emergency" to complete the financing of the wall on the border with Mexico to fight illegal immigration.

He said the president "said he was ready to sign" a compromise compromise reached between Democrats and Republicans to avoid a new "closure" of government departments.

"A national emergency will be announced at the same time," he said, adding that he supports this measure, which allows the president to bypass Congress to raise funds.

Democratic House Speaker Nancy Pelosi responded to Trump's assertion that what happened on Mexico's borders did not call for a state of emergency.

"We will consider the appropriate response if Trump declares the state of emergency," she said.