WASHINGTON: An embattled Donald Trump fired his government's chief lawyer for refusing to defend his controversial immigration orders Monday, deepening a political crisis engulfing his young presidency.

In a caustic statement, Trump's White House said acting attorney general Sally Yates had "betrayed" the Department of Justice in defying Trump and had been relieved of her duties with immediate effect.

Yates -- a career prosecutor promoted by Barack Obama and held over by Trump pending confirmation of his own nominee, Jeff Sessions -- had refused to mount a legal defense of Trump's ban on immigration from seven Muslim nations.

In a memo to Department of Justice staff, she expressed doubts about the legality and morality of Trump's decree.

"My responsibility is to ensure that the position of the Department of Justice is not only legally defensible, but is informed by our best view of what the law is," Yates wrote.

"I am not convinced that the defense of the executive order is consistent with these responsibilities nor am I convinced that the executive order is lawful," she added.

"For as long as I am the acting attorney general, the Department of Justice will not present arguments in defense of the executive order, unless and until I become convinced that it is appropriate to do so."

In the end, her tenure lasted only a few more hours.

The White House hit back quickly, accusing Yates of being "weak on borders and very weak on illegal immigration."

Trump replaced Yates with Federal prosecutor Dana Boente, as he awaits the confirmation of his nominee, Senator Sessions, by the Senate.

But it was a defiant and damaging parting shot for a president already facing multiple lawsuits and worldwide opprobrium. Trump's executive order suspended the arrival of all refugees for a minimum of 120 days, Syrian refugees indefinitely and bars citizens from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen for 90 days.

Several federal judges have since filed temporary stays. On Sunday, attorneys general from 16 US states, including California and New York, condemned Trump's directive as "unconstitutional" and vowed to fight it.

- 'Monday night massacre' -

Trump's furious response may have lasting political repercussions, not least making Sessions' Congressional confirmation more complicated.

He faces a vote on the Senate Judiciary Committee Tuesday and then has to be confirmed by the full Senate before taking up the post.

Congress' top Democrat, Senator Chuck Schumer said Yates' firing underscored how important "it is to have an Attorney General who'll stand up to the White House when they violate the law."

There are calls for Sessions to face more hearings. The issue also risks overshadowing Trump's announcement of his pick to fill an empty chair on the Supreme Court.

That announcement had already been moved forward two days to Tuesday evening as the administration tried to move past the crisis.

Democratic lawmakers have vociferously opposed Trump's immigration order and Republicans are privately seething over the way his White House has handled the issue.

In a separate decision announced without explanation by Homeland Security Secretary John Kelly, Trump also replaced acting Immigration and Customs Enforcement director Daniel Ragsdale.

Two dismissals in one night held uncomfortable echoes of President Richard Nixon's "Saturday night massacre" during the Watergate scandal.

Then, Nixon fired the special prosecutor investigating him, prompting the departures of his attorney general and deputy attorney general.

The events catalyzed Nixon's impeachment.

Even before Monday night's drama, Trump had been struggling to contain the political fallout from his immigration ban.

- 'American values' -

In remarks at the White House and on Twitter, Trump variously tried to play down the impact of the order and defended the White House's decision not to give advance warning to border guards, diplomats and travelers.

"If the ban were announced with a one week notice, the 'bad' would rush into our country during that week. A lot of bad 'dudes' out there!" Trump claimed.

For many in Trump's orbit, he is merely carrying out election promises.

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 released Monday.

But after a weekend of chaos at airports, mass protests and diplomatic outcries, criticism even came from Trump's predecessor Barack Obama, who broke his silence for the first time since leaving office.

"President Obama is heartened by the level of engagement taking place in communities around the country," spokesman Kevin Lewis said, adding that "American values are at stake" and noting Obama rejects faith-based discrimination.

Senior national security officials from the Obama and George W. Bush administrations warned in a letter to top Trump cabinet members that the order "will do long-term damage to our national security."

Calling the measure a tragically "unnecessary" move that will fuel violent extremist propaganda, they said it "sent exactly the wrong message to the Muslim community here at home and all over the world: that the US government is at war with them based on their religion."

Late Monday, a few thousand people chanted slogans and held up banners in front of the Supreme Court, which could ultimately rule on the measure. -AFP