US President Donald Trump has lashed out at top Republican Paul Ryan for criticising his earlier statements about revoking birthright citizenship.
The term refers to the automatic right to citizenship for children born in the US, even to non-citizens.
Mr Trump said the soon-to-retire House of Representatives Speaker should not be opining on “something he knows nothing about”.
The president’s idea has met a mixed reception from his fellow Republicans.
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On Wednesday, Mr Trump took to Twitter to vent his ire at the most powerful congressional Republican.
Paul Ryan should be focusing on holding the Majority rather than giving his opinions on Birthright Citizenship, something he knows nothing about! Our new Republican Majority will work on this, Closing the Immigration Loopholes and Securing our Border!
— Donald J. Trump (@realDonaldTrump) October 31, 2018
Next week Americans go to the polls for the mid-term elections. Republican control of both houses of Congress is up for grabs.
The president also tweeted about Democrat Harry Reid, who in 1993 called for the end of the birthright policy. Mr Reid has apologised repeatedly since making those remarks.
On Tuesday, Mr Ryan, who will retire in January, had challenged the president’s statements, saying he “obviously” could not just end the policy.
Mr Ryan has clashed with the president over issues – including healthcare and immigration – several times, and reportedly found working with him to be frustrating.
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“You cannot end birthright citizenship with an executive order,” Mr Ryan told Kentucky-based radio station WVLK.
“We didn’t like it when Obama tried changing immigration laws via executive action, and obviously as conservatives, we believe in the constitution.”
Mr Trump had earlier called the birthright policy “ridiculous” and incorrectly claimed the US was the only country to offer it. In fact, a number of countries including Canada and Mexico have the same practice.
He said he would change the US constitution’s 14th amendment, which gives citizenship to all born on US soil, via an executive order.
Republican Senator Lindsey Graham of South Carolina was quick to express his support for Mr Trump’s plan.
In a series of tweets, Mr Graham called birthright citizenship an “absurd policy”, saying he has always supported eliminating it.
The United States is one of two developed countries in the world who grant citizenship based on location of birth.
This policy is a magnet for illegal immigration, out of the mainstream of the developed world, and needs to come to an end.
— Lindsey Graham (@LindseyGrahamSC) October 30, 2018
Senator Ted Cruz, who is currently facing a strong challenge from Beto O’Rourke in Texas, also agreed with the president, according to the Dallas News.
But some conservatives have said the president’s comments have endangered Republicans in tight mid-term election races against Democrats.
And Mr Ryan was not the only Republican to shy away from changing the constitution.
Representative Carlos Curbelo, a Republican who is up for re-election in his Miami, Florida district, tweeted: “Birthright citizenship is protected by the Constitution, so no @realDonaldTrump you can’t end it by executive order.”
Mike Coffman of Colorado, another Republican congressman facing a tough re-election, also called out the president on Twitter.
“We have a Constitution. The President should take heed and follow it.”
I hate to break the news to President Trump, but the Supreme Court isn’t going to let him rewrite immigration law by executive fiat, nor should they. We have a Constitution. The President should take heed and follow it.
— Rep. Mike Coffman (@RepMikeCoffman) October 30, 2018
Utah Republican Mia Love said in a statement she has “always opposed Presidential attempts to change immigration law unilaterally”.
“The 14th Amendment makes the conditions of citizenship clear: individuals born in this country are citizens,” the congresswoman, who is the daughter of Haitian immigrants, said.
The president’s critics have dismissed the move as political grandstanding ahead of the mid-terms.
Top Democrat Nancy Pelosi called Mr Trump’s claim an example of “Republican’s spiralling desperation to distract from their assault” on healthcare.
But Indiana Senator Joe Donnelly, a vulnerable Democrat up for re-election, opted for a more open stance, saying he would want to review any proposed legislation first.
According to a 2015 Pew Research Centre poll, 60% of Americans were against ending birthright citizenship.
Looking at party divides, however, showed that 53% of Republicans polled on the issue supported amending the constitution regarding the policy.