The US Justice Department on Friday filed a brief notice saying it would appeal a Maryland federal judge's ruling that halted a key portion of President Donald Trump's revised immigration order which was set to take effect one day before, China's Xinhua news agency reported.

The Justice Department has not yet filed its formal appeal in the Fourth Circuit Court of Appeals, located in Richmond, Virginia, where the case will eventually be heard, said local media reports.

The ruling in Maryland and another in Hawaii earlier this week claimed Trump's temporary barring U.S. entry to global refugees and immigration from six predominantly Muslim countries in the Middle East and Africa violated the First Amendment of the US Constitution, citing statements by Trump and his advisers suggesting the real purpose of the disputed immigration order was to discriminate against Muslims.

The Trump administration denied it is a Muslim ban, arguing the order aims to prevent terrorism by suspending visitors from terror-prone countries where visa vetting may not be effective.

So far the US Justice Department didn't move to appeal the Hawaii federal judge's ruling, which would bring the case to the same San Francisco-based Ninth Circuit Court of Appeals that rejected an earlier version of the immigration order.

Hours after the Hawaii federal judge's ruling on Wednesday, Trump slammed it as "an unprecedented judicial overreach", pledging to take the legal fight all the way to the Supreme Court.

"We're going to take our case as far as it needs to go, including all the way up to the Supreme Court," Trump said Wednesday night at a campaign rally in Nashville, the state of Tennesse, suggesting the ruling was made for "political reasons."

Derrick Watson, the federal judge in Hawaii, noted that Trump's adviser Stephen Miller said on Fox News last month that the revised order was intended to have "the same basic policy outcome" as the first one, aside from a few changes designed to bolster the administration's legal standing.

In the Maryland case, federal judge Theodore Chuang wrote that the origins of Trump's immigration order suggests that religious screening, not national security, was the primary purpose.

Under President Trump's order, a 90-day ban on travel to the US will be imposed on citizens of Iran, Libya, Syria, Somalia, Sudan and Yemen, while freezing refugee resettlement for four months.

-- BERNAMA