Washington • President Donald Trump vowed Wednesday to push forward with his call to end birthright citizenship, despite a backlash from legal scholars and some prominent members of his own party to his pledge a day earlier to take executive action on the matter.

In morning tweets, Trump said he would end the 150-year-old practice “one way or the other,” seeming to leave the door open to either congressional action or a constitutional amendment, which many legal scholars say would be necessary to achieve his aims.

Trump also said the issue would ultimately be decided by the Supreme Court.

Trump is seeking to end the long-standing right to U.S. citizenship for children born to noncitizens in the United States, a policy that he said in his tweets "costs our Country billions of dollars and is very unfair to our citizens."

On Tuesday, leading Democrats and immigrants rights activists blasted Trump's pledge to issue an executive order, and House Speaker Paul D. Ryan, R-Wis., dismissed the idea during a radio interview, saying it is not consistent with the 14th Amendment of the Constitution.

Senate Judiciary Committee Chairman Charles E. Grassley, R-Iowa, meanwhile, said the issue is one on which Congress, rather than the president, should take the lead.

In his Wednesday tweet, Trump asserted that birthright citizenship is not subject to the 14th Amendment because of the inclusion of the phrase "subject to the jurisdiction thereof."

Legal experts have debated for years how to interpret the citizenship clause of the 14th Amendment, but the consensus is one-sided: Most agree that it in fact grants citizenship to those born on U.S. soil.

The first section of the amendment says: "All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside."

Some legal scholars argue that the phrase "and subject to the jurisdiction thereof" seems to give the government some leeway to restrict the right, just as other constitutional principles can be limited. But the mainstream opinion from both right and left is that it is more likely that a constitutional amendment, rather than federal legislation or an executive order, would be needed to change the birthright conferred on people born here.

In his latest tweets, Trump also highlighted a view expressed by then-Sen. Harry M. Reid in 1993 that "no sane country" would award citizenship to children of undocumented immigrants born on its soil. Reid, a Democrat, reversed his position in 1999, at which time he apologized for his earlier stance.

"Many legal scholars agree . . . Harry M. Reid was right in 1993, before he and the Democrats went insane and started with the Open Borders (which brings massive Crime) 'stuff,'" Trump wrote.

In one of his tweets, Trump also said that the term "anchor babies," which has been used to describe children of noncitizens born in the United States, is "nasty." Trump has often used the term himself.

The Washington Post’s Robert Barnes contributed to this report.