A federal judge in Seattle partially blocked US President Donald Trump's newest restrictions on refugee admissions on Saturday, the latest legal defeat for his efforts to curtail immigration and travel to the US.

The decision by US District Judge James Robart is the first judicial curb on rules the Trump administration put into place in late October that have contributed significantly to a precipitous drop in the number of refugees being admitted into the country.

Refugees and groups that assist them argued in court that the administration's policies violated the Constitution and federal rulemaking procedures, among other claims.

Department of Justice attorneys argued in part that US law grants the executive branch the authority to limit refugee admissions in the way that it had done so.

On Sunday, the Trump administration effectively paused refugee admissions from 11 countries mostly in the Middle East and Africa, pending a 90-day security review, which was set to expire in late January.

The countries subject to the review are Egypt, Iran, Iraq, Libya, Mali, North Korea, Somalia, South Sudan, Sudan, Syria and Yemen.

A Reuters review of State Department data showed that as the review went into effect, refugee admissions from the 11 countries plummeted.

Robart ruled that the administration could carry out the security review, but that it could not stop processing or admitting refugees from the 11 countries in the meantime, as long as those refugees have a "bona fide" connection to the US.

As part of its new restrictions, the Trump administration had also paused a program that allowed for family reunification for refugees, pending further security screening procedures being put into place.