Trump to deploy National Guard to secure border with Mexico

US President Donald Trump will sign an executive order asking the National Guard to secure his country's border with Mexico so as to immediately prevent caravans of illegal immigrants crossing into America.

"The threat is real," Homeland Security Secretary Kirstjen Nielsen told reporters at a White House news conference.

"We continue to see unacceptable levels of illegal drugs, dangerous gang activity, transnational criminal organisations and illegal immigration flow across our border," she said.

"This threatens not only the safety of American communities and children but also the very rule of law, on which, the country was founded. It's time to act. So let's talk a little bit about that today," she said.

"In an effort to prevent such a consequence, the president has directed that the Department of Defence and the Department of Homeland Security work together with our governors to deploy the National Guard to our southwest border to assist the Border Patrol," she said.

Nielson asserted that Trump would sign a proclamation to that effect today.

"It's time to act," she added.

In the last 15 months, she said, the Trump administration has taken major steps to methodically strengthen border security.

"We stepped up the targeting of dangerous criminal gangs such as MS-13, we removed thousands more criminal aliens than the year prior, we no longer exempt entire classes of illegal aliens from the consequences of breaking our immigration laws," she said.

"We began the first new border wall system construction in close to a decade, we modified our asylum system processing to more quickly adjudicate claims and we ended so-called temporary immigration programs that were either constitutionally dubious or were administered in a manner that was inconsistent with the purpose of the law or contrary to the intent of Congress," Nielson said.

She said that despite a number of actions, there has been a rise in the numbers of illegal border crossings from 40-year lows last April to previous levels.

"Our current border security and immigration laws fail the American people," she said.

Ruing that the system rewards bad behaviour, she said it does not punish lawbreakers.

"It undermines our nation's economic interests. Make no mistake, interdiction without the ability to promptly remove those without legitimate cause is not border security, it is not national security," she asserted.

Nielsen said that the Congress has failed to act.

"Worse still, some members of Congress have continually opposed efforts to secure the border. As a result of this continued congressional inaction, the administration has drafted legislation, and we will be asking Congress again to provide the legal authority and resources to address this crisis at our borders," she added.

"We will not allow illegal immigration levels to become the norm. More than 1,000 people a day, 300,000 a year, violating our sovereignty as a nation will never be acceptable to this president," she said.

Asking the Congress to pass the necessary legislation, Nielsen said in the meantime, Trump has directed that National Guard personnel be deployed to the southern border.

"While plans are being finalised, it's our expectation that the National Guard will deploy personnel in support of CBP's border security mission. It will take time to have the details in place, but we are beginning today and we are moving quickly. We are anxious to have the support," Nielsen said.