Republican presidential nominee Donald Trump linked illegal immigration and employment Saturday, pledging to start deporting offenders as soon as he is sworn in should he become the White House's next occupant.

Trump all the while courted the black vote, claiming that the shooting of basketball star Dwyane Wade's cousin will make African Americans support him, but the move instead triggered a firestorm of criticism.

"On Day One, I am going to begin swiftly removing criminal illegal immigrants from this country - including removing the hundreds of thousands of criminal illegal immigrants that have been released into US communities under the Obama-Clinton administration," Trump told supporters in Des Moines, Iowa.

Trump's Democratic rival Hillary Clinton served as secretary of state during President Barack Obama's first term in office. The next president will be sworn in on January 20.

"I am going to build a great border wall, institute nationwide e-verify, stop illegal immigrants from accessing welfare and entitlements and develop an exit-entry tracking system to ensure those who overstay their visas are quickly removed," Trump warned.

Details of Trump's immigration policies remain scant. He rallied much of his primary support with a controversial hardline tone against illegal immigrants and his plan to build a wall on the Mexican border.

Some of his advisors are now reportedly urging him to tone down his signature policy priority.

Earlier, former Alaska governor Sarah Palin has warned Trump of "massive disappointment" if he does not follow through with his promise to deport the 11 million undocumented immigrants currently living in the US.

But he recently walked back his stance and has suggested a "softening" in his immigration position in a Fox News town hall with Sean Hannity. Trump proposed that "the good ones" – law-abiding undocumented immigrants – can stay in the US if they "pay back-taxes".