A US federal judge has blocked Donald Trump's attempt to end birthright citizenship for children born to parents who are in the country illegally or temporarily.

"Today, virtually every baby born on US soil is a US citizen upon birth," Maryland district judge Deborah Boardman ruled on Wednesday. "That is the law and tradition of our country."

The ruling extends the existing pause on Trump's 20 January executive order until the legal process plays out, which could take months or even years.

The Trump administration can appeal against the ruling and is expected to do so, say experts.

Ending birthright citizenship has long been an aim of President Trump as part of his drive to remove illegal immigrants from the US.

His order, which was scheduled to come into effect on 19 February, would have withheld automatic citizenship rights from newborns if neither of their parents were US citizens or lawful permanent residents.

The challenge to the executive order was brought by two immigrant rights groups that filed the lawsuit on behalf of five pregnant women.

On Wednesday, the federal judge ruled that Trump's order "runs counter to our nation's 250-year history of citizenship by birth".

"The United States Supreme Court has resoundingly rejected the president's interpretation of the Citizenship Clause of the 14th Amendment," she said. "In fact, no court in the country has ever endorsed the president's interpretation. This court will not be the first."

The ruling comes two weeks after a federal judge in Seattle called Trump's order "blatantly unconstitutional" and issued a 14-day restraining order. That ruling will expire on Thursday, when that judge will hold another hearing.

At the heart of the case is the interpretation of the 14th Amendment to the US Constitution, adopted shortly after the Civil War, which states in part: "All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States".

The Trump administration argues that the clause excludes children of non-citizens who are in the US unlawfully, and added that the order is "an integral part" of the president's goal to address the country's "broken immigration system and the ongoing crisis at the southern border".

But since the late 19th Century the amendment has been interpreted by courts including the US Supreme Court as automatically granting citizenship rights to children born on US soil, with a few exceptions such as the children of diplomats.

According to 22 Democratic state attorneys general who have brought lawsuits to stop Trump's policy, more than 150,000 babies would be denied citizenship each year under the executive order.