"Guess what? You don't", Trump said. Conservatives have argued the citizenship provision for children applies only to those born to legal USA citizens.
The 14th Amendment has its roots in slavery.
FILE - In this October 27, 2018, file photo, President Donald Trump pauses while speaking at a rally at Southern Illinois Airport in Murphysboro, Ill.
"We're the only country in the world where a person comes in and has a baby, and the baby is essentially a citizen of the United States", Trump said.
The move, which many legal experts say contradicts the Constitution, would be the boldest yet by a president elected to office pledging to take a hard line on immigration, an issue he has revived before next week's midterm elections.
Mr. Ryan said it is hypocritical for a Republican president to do what the GOP complained about under President Obama in using executive powers to try to rewrite immigration law.
What does the end of birthright citizenship mean?
Mattis warns Khashoggi murder "must concern us all greatly"
Central Intelligence Agency director Gina Haspel was in Turkey earlier this week to review evidence, and she briefed U.S. Turkish officials suspect Saudi agents killed Khashoggi, 59, inside the consulate and cut up his body.
When quizzed over whether his new policy would face legal challenges, the billionaire businessman turned politician said: "It was always told to me that you needed a constitutional amendment".
However, the order has seen widespread backlash amid claims it is against the Constitution.
Under current policy, anyone born in the US - regardless of whether they are delivered by a non-citizen or undocumented immigrant - is considered a citizen.
Changing an amendment in the Constitution would require the support of two-thirds of the US House of Representatives and the Senate and the backing of three-fourths of US state legislatures at a constitutional convention. "You don't", Trump said.
"By directly mentioning the role of the states, the 14th Amendment greatly expanded the protection of civil rights to all Americans and is cited in more litigation than any other Amendment", according to the Library of Congress.
Congress has all but abandoned their duty to make law in this area, punting the ball to the executive branch where the application of the law varies with whoever happens to be occupying the White House in the moment. She also believes the Supreme Court would ultimately deem an executive order of this nature unconstitutional. "We are on the heels of election so he is saying anything to get a few more votes", she said.