By Julia Edwards Ainsley and Richard Cowan

WASHINGTON (Reuters) - Divisions have emerged among advisers to President Donald Trump over whether to rescind a signature policy of his predecessor, President Barack Obama, that shields young immigrants from deportation, according to congressional sources and Republicans close to the White House.

Even though Trump campaigned on a promise to roll back Obama's executive orders on immigration, the Republican has so far left intact an order safeguarding 750,000 people who were brought to the United States illegally as children, known as the "dreamers."

The issue has become a flashpoint for White House advisers divided between a more moderate faction such as chief of staff Reince Priebus and immigration hardliners Stephen Miller and Steve Bannon, said a former congressional aide who has been involved with immigration issues in Washington.

Priebus has said publicly that Trump will work with Congress to get a "long-term solution" on the issue.

Meanwhile, Miller, said to have mastered the thinking of his former boss and anti-immigration advocate Jeff Sessions, Trump's nominee for U.S. Attorney General, as well as Bannon, former head of right-wing Breitbart News, have pushed Trump to take a harder approach and rescind the protections.

Two officials at the Department of Homeland Security expect Trump to simply stop renewing the authorizations that "dreamers" currently have to work, drive and obtain higher education. Under that plan, the most recently renewed authorizations would expire in two years.

But a senior House Republican aide said it was uncertain whether the administration had scrapped the idea of overturning Obama's Deferred Action for Childhood Arrivals, known as DACA, as the internal debate plays out.

Preserving DACA has also become somewhat of a bartering chip as Trump seeks congressional support for a wall on the U.S.-Mexico border and other early administration priorities.

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The White House is "acutely aware" of the firestorm in the country and within Congress that could swamp the fledgling administration just as it plunges into negotiations over the wall, healthcare, tax reform and infrastructure investments, said the senior House Republican aide.

Another congressional aide described a Senate bill sponsored by Democrat Dick Durbin and Republican Lindsey Graham to protect the "dreamers" as the "sugar that would help the medicine of the wall go down."

The bill would likely face challenges winning enough votes to pass. Efforts to attach some tough conservative amendments could lose Democratic Party support and sink the whole effort.

Trump has kept his public comments on DACA vague.

In an interview with ABC News on Wednesday, Trump said his administration would be coming out with a policy to deal with "dreamers" over the next four weeks.

"They shouldn't be very worried. They are here illegally. They shouldn't be very worried. I do have a big heart. We're going to take care of everybody. We're going to have a very strong border," Trump said in the interview with ABC.

Trump reportedly told Durbin during the inaugural luncheon at the Capitol on Jan. 20 that he did not have to worry about an executive action overturning Obama's order.

But there is scant trust among Democrats that Trump will keep his word. And immigration advocates said DACA recipients live in fear and uncertainty as the message from the White House and Republicans seems to shift by the day.

House Speaker Paul Ryan told a woman protected by DACA, at a townhall hosted by CNN Jan. 12, that there should be a solution for people like her to get "right with the law" and not be separated from their families.

Just two days prior, Sessions, a Senator, told a Senate panel considering his confirmation that it would "certainly be constitutional" to repeal DACA.

Sessions also attempted to force a vote to block DACA in the Senate in 2014.

Miller, Sessions' former staffer, is now Trump's senior adviser for policy at the White House. Miller is known to be a staunch advocate for restricting immigration, even by workers who enter legally on visas.

Both Miller and Bannon, Trump's senior counselor and chief strategist, are seen as outsiders to the Republican establishment and unafraid to upset people like Ryan to stay true to Trump campaign promises.

Priebus, however, came to the White House after chairing the Republican National Committee and has spent years seeking to unify the party and cultivating relationships with career politicians.

(Reporting by Julia Edwards Ainsley and Richard Cowan; Editing by Caren Bohan and Grant McCool)