The Republican candidate has outlined his immigration policies amid accusations he has 'flip-flopped' on the issue
Donald Trump has pledged to to introduce a 'tracking system' for illegal immigrants if he is elected as US president.
Speaking at a rally in Iowa, Mr Trump vowed to begin "swiftly removing criminal illegal immigrants" from "day one" if he is elected.
"We will use immigration law to prevent crimes, and will not wait until some innocent American has been harmed or killed before taking action," he explained.
"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.
"If we don’t enforce visa expiration dates, then we have an open border - it’s as simple as that," he added.
Hillary Clinton has frequently criticised her rival's comments on immigration.
In a statement on Mr Trump's earlier pledge to deport millions of immigrants, the Clinton campaign said: "Donald Trump must stop playing games with the lives of law-abiding immigrant families in order to save his campaign.
"These are families who contribute to the greatness of our country and that need a President who will fight to keep them together - not someone who will denigrate them and tear them apart.”
Both Mrs Clinton and Mr Trump have accused each other of bigotry in recent speeches.
Mr Trump has also been criticised for apparently 'flip-flopping' or toning down his policies on immigration in recent days - although the candidate himself has insisted that is not the case.