WASHINGTON — US President Donald Trump has crushed the most defiant display yet of official opposition to his immigration and refugee restrictions -- but resistance continued to spread on Tuesday, inside and outside the government.

Trump’s swift dismissal of acting attorney general Sally Yates for refusing to defend his executive order capped a night of high drama, Washington-style, that drew comparisons with a flurry of urgent housekeeping by Richard Nixon at the height of the Watergate scandal.

Trump came out fighting on Tuesday, hitting out at Democrats for stalling on the approval of his nominee for attorney general and the rest of his cabinet.

"They should be ashamed of themselves! No wonder D.C. doesn’t work!" Trump wrote on Twitter.

But as the president defended his move to bar entry for people from seven mainly Muslim countries and halt the US refugee resettlement programme, challenges were mounting on all sides -- from the United Nations to lawmakers in his Republican Party.

UN Secretary-General Antonio Guterres sharpened his criticism of the ban, calling it a "blind" measure that was more likely to fan extremist propaganda than combat the threat of terrorism.

And as former national security officials warned that the order sends exactly the wrong message to Muslims -- that America is at war with them over their faith -- even US diplomats jumped into the fray in a rare display of dissent in an administration just a week old.

Keeping ’bad people’ out 

Trump’s order bars US entry for travellers from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen for 90 days. It also suspends the arrival of all refugees for at least 120 days, and Syrian refugees indefinitely.

It has led to the detention of more than 100 people at US airports and mass protests in many cities, and raised howls of protests abroad.

White House spokesman Sean Spicer pushed back once more on Tuesday against the tide of criticism.

"This is not a Muslim ban. It’s not a travel ban," he told reporters. "It’s a vetting system to keep America safe. That’s it. Plain and simple."

Trump received a vote of support Tuesday from House of Representatives speaker Paul Ryan, who defended the restrictions as a legitimate way to keep out potential terrorists.

"There is nothing wrong with taking a pause and making sure we had the proper vetting standards in place so that we do not have a problem like France had with Paris," Ryan said, alluding to November 2015 suicide bombings and shootings that left 130 people dead in the French capital.

The measure also appears popular with Trump’s base: around 48 percent of Americans support a freeze on immigration from "terror prone" regions, even if it means turning refugees away, according to a Quinnipiac poll.

One of them is Don Krepps, a retired construction worker in rural Ohio, 66, who voted for Trump.

"He tries to keep the bad people from coming in that don’t belong here," he said.

Krepps gives short shrift to the arguments of the opposition: "If they would leave him alone, I think he would do okay, but Democrats complain about everything he does."

To the Supreme Court? 

The challenges have been coming from all sides.

Critics including in Trump’s own camp complain that the order is too broad and was rolled out hastily, reportedly without consultation with key officials who would be tasked with overseeing it.

Homeland Security Secretary John Kelly insisted Trump’s top advisors were not caught unawares by the unveiling of the order, saying "high-level folks in the government, attorneys as well" were consulted on the draft.

Possibly the most dramatic gesture of protest to date came from Yates, who instructed Department of Justice attorneys Monday not to defend Trump’s order in court, expressing doubts about its legality and morality. Trump wasted no time in crushing the rebellion.

Yates -- an Obama appointee held over pending confirmation of Trump’s nominee Jeff Sessions -- was sacked within hours and replaced by federal prosecutor Dana Boente, who vowed to defend Trump’s directive.

Legal challenges to the ban look set to loom large during confirmation hearings for Trump’s Supreme Court nominee, whose name will be revealed Tuesday night.

Several federal judges have already filed temporary stays against the decree’s implementation and attorneys general from 16 US states, including California and New York, have vowed to fight it as "unconstitutional."

- ’Unnecessary’ -

At the State Department, meanwhile, diplomats declared their opposition in a "dissent memo" delivered through an official channel.

According to leaked drafts of the memo, they argued the move is a betrayal of American values.

"We are better than this ban," they declare.

The rumblings drew a scathing riposte from Spicer, who said of the diplomats, "I think they should either get with the program or they can go."

Senior national security officials from the Barack Obama and George W. Bush administrations warned in a letter to top Trump cabinet members that the order will do long-term damage to US national security, calling it a tragically "unnecessary" move that will fuel violent extremist propaganda.

And according to industry sources, a broad coalition of US technology firms -- including Google parent Alphabet, Netflix, Airbnb and Twitter -- is planning a joint legal strategy challenging Trump’s order, which is expected to have a large impact on a sector that employs thousands of immigrants. — AFP