A US district court judge in Hawaii yesterday blocked US President Donald Trump's new ban on travellers from six Muslim-majority countries, just hours before it was due to take effect.

In issuing a temporary restraining order of Trump's executive order, judge Derrick Watson said those challenging US President Donald Trump's travel ban would likely be successful in their claim that it violates the constitution's ban on religious discrimination.

"Plaintiffs have shown a strong likelihood of succeeding in their claim that the Executive Order violates First Amendment rights under the constitution," he wrote.

Ismail Elshikh, an imam at a Hawaii mosque, had challenged Trump's order, claiming that it prevented his Syrian mother-in-law from joining his family in Hawaii, "denying them their right, among other things, to associate with family members overseas on the basis of their religion and national origin," court documents showed.

Elskhikh challenged the policy along with the state of Hawaii, which says it will harm the Pacific island state.

Separate legal challenges were also underway in Washington state and Maryland.

An earlier version of Trump's order had also been suspended last month after causing chaos at airports around the world and setting off a wave of protests.

Trump: legal concerns addressed

Trump's new action, due to take effect today, had attempted to ban tourist, immigration and most other entries to the United States from six countries for 90 days - Iran, Libya, Somalia, Sudan, Syria and Yemen - but removed Iraq from the list of countries affected.

It had also ordered the US refugee programme be suspended for 120 days though an indefinite ban on refugees from Syria was no longer included.

The executive order cites presidential powers under the Immigration and Nationality Act and says the measures are needed "to protect the nation from terrorist activities by foreign nationals admitted to the United States.

A Pew Research Center analysis of State Department data showed 2,466 refugees from the six countries under new travel restrictions have resettled in the United States since Trump became president in January.

The refugees make up about a third of all refugees admitted since his Jan 20 inauguration.

Meanwhile the Trump administration believed it had addressed the legal concerns in the new order.

"Let me tell you something, I think we ought to go back to the first one and go all the way," Trump said at the Nashville rally, calling the new order a "watered-down" version of the original policy.

"The danger is clear, the law is clear, the need for my executive order is clear."

- dpa