ANALYSIS: Staunch conservative allies of US President Donald Trump have erupted in anger and incredulity after Democrats announced the president had agreed to pursue a legislative deal that would protect thousands of young undocumented immigrants from deportation but not secure Trump's signature campaign promise: building a massive wall along the US-Mexico border.

As midnight neared, social media accounts came alive as elected officials and activists on the right dashed off tweets and posts to share their shock.

And in between those posts, there was a flurry of fuming calls and text messages - a blaring political fire alarm among Trump's diehard supporters.

REUTERS Has US President Donald Trump done an about-face on immigration? His staunchest allies think he has.

"The reality is sinking in that Trump administration is on the precipice of turning into an establishment presidency," Sam Nunberg, a former Trump campaign adviser, said in an interview early Thursday morning.

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While the initial wave of fury could change direction as new details emerge, the torrent represented the first major break of Trump's devoted base from the president on a core issue.

REUTERS Republican Steve King reckons Trump's base has been destroyed beyond all repair.

Republican Steve King, one of the GOP's biggest immigration hawks, issued a dramatic warning to the president after he scrolled through news reports.

"If AP is correct, Trump base is blown up, destroyed, irreparable, and disillusioned beyond repair," King tweeted, referencing an Associated Press story on the bipartisan agreement.

Conservative radio talk show host Laura Ingraham, who is friendly with Trump, mocked him for seeming to shelve the pledge that has animated his supporters since his campaign's launch.

REUTERS US President Donald Trump tried to counter the backlash but denying a deal on DACA.

"BUILD THE WALL! BUILD THE WALL!"...or...maybe...not really. — Laura Ingraham (@IngrahamAngle) September 14, 2017



"Exactly what @realDonaldTrump campaigned on. Not," Ingraham wrote on Twitter. She later added, "BUILD THE WALL! BUILD THE WALL! ??? or ... maybe ... not really."



"Deep State Wins, Huge Loss for #MAGA," Fox Business anchor Lou Dobbs tweeted, alluding to Trump's "Make America Great Again" campaign slogan.



Trump tried to ease the GOP backlash in a series of tweets that insisted the border wall "will continue to be built" and that no deal was hashed out with Democrats on the so-called undocumented "dreamers."



"No deal was made last night on DACA. Massive border security would have to be agreed to in exchange for consent. Would be subject to vote," Trump wrote, referring to Deferred Action for Childhood Arrivals, or DACA, an Obama-era programme that has allowed 690,000 dreamers to work and go to school without fear of deportation.

Despite the denials on the deal, Trump had also appeared to acknowledge the complexity of handing the issue of "dreamers', tweeting: "They have been in our country for many years through no fault of their own - brought in by parents at young age".



Right-wing commentator and author Ann Coulter, who wrote 2016's In Trump We Trust, lashed out at the President's comments, tweeting: "At this point, who DOESN'T want Trump impeached?"

REUTERS Former White House chief strategist Steve Bannon says GOP voters will lose enthusiasm for Trump if he drifts to the centre on immigration.

At this point, who DOESN'T want Trump impeached? https://t.co/g1mMhmm8ng — Ann Coulter (@AnnCoulter) September 14, 2017

If we're not getting a wall, I'd prefer President Pence. https://t.co/g1mMhmm8ng — Ann Coulter (@AnnCoulter) September 14, 2017

REUTERS US House of Representatives Speaker Paul Ryan says there was no deal reached between President Donald Trump and congressional Democratic leaders on DACA.





Breitbart News, the conservative website now run by former White House chief strategist Stephen Bannon, quickly became a gathering place for aggrieved Trump backers. Readers congregated by the thousands in the comments section for an article with a bright red headline: "Amnesty Don."



Days earlier, Bannon said on CBS's 60 Minutes that he was "worried about losing the House now because of this, because of DACA," arguing that Republican voters would lack enthusiasm for Trump and the party if they felt it was drifting to the centre on immigration.



"If this goes all the way down to its logical conclusion, in February and March it will be a civil war inside the Republican Party that will be every bit as vitriolic as 2013," Bannon said, referencing the stalled fight that year over a comprehensive immigration bill. "And to me, doing that in the springboard of primary season for 2018 is extremely unwise."

"This a betrayal of the highest order," a Breitbart editor, who was not authorised to speak publicly, said in a phone call late Wednesday. "Donald Trump should be ashamed of himself. He wasn't elected to do this."

The editor was mostly echoed by the site's readers:

"Put a fork in Trump. He is done."

"PRIMARY TIME!!!!"

"What a HUGE let down."

"I can reconcile Trump caving on virtually any issue, Amnesty and not building the wall are not one of them."

Others who have supported Trump's immigration positions took a wait-and-see approach amid the chaos.

"My sense is that he told Chuck and Nancy what they wanted to hear, and they heard what they wanted to hear. I think there could be some mischief-making on the part of Schumer since the White House is walking it back," said Mark Krikorian, an immigration hard-liner who runs the Centre for Immigration Studies, in an interview.

Meanwhile, Fox News host Sean Hannity, who is in regular contact with Trump, directed his ire over the developments not at the president but at GOP leaders on Capitol Hill.

"Well Mitch GREAT JOB!" Hannity tweeted, referring to Senate Majority Leader Mitch McConnell, R-Ky. "You failed so miserably with Healthcare and 'excessive expectations' now @POTUS has to deal with Dem Leaders!"

Hannity added later, "I blame R's. They caused this. They wanted him to fail and now pushed him into arms of political suicide - IF TRUE."