Tensions are flaring between the White House and a moderate Republican senator who claimed a young Trump aide was standing in the way of a bipartisan deal on immigration reform.

South Carolina Sen. Lindsey Graham, a longtime advocate of comprehensive immigration reform that leans in the direction of Democrats, blasted hardline Trump-whisperer Stephen Miller Sunday as a meddlesome 'outlier.'

The White House fired back, using the same word to describe Graham in a Washington version of 'I know you are, but what am I?"

Graham's complaint is that Miller, 32, has long been undercutting Trump's ability to cut a deal that might have made Friday's government shutdown unnecessary.

'As long as Stephen Miller is in charge of negotiating immigration, we are going nowhere. He's been an outlier for years,' Graham told reporters at the Capitol on Sunday.

'As long as Stephen Miller is in charge of negotiating immigration, we are going nowhere,' Republican Sen. Lindsey Graham said

Miller, 32, is generally thought to be the unseen force nudging the president toward hardline immigration policies

'I've talked with the president. His heart is right on this issue. He's got a good understanding of what will "sell." And every time we have a proposal, it is only yanked back by staff members.'

Miller came to the White House from the Senate, where he staffed then-Republican Senator Jeff Sessions on immigration issues.

His claim to fame was helping Sessions kill a bipartisan effort in 2013 to put millions of illegal immigrants on a pathway to citizenship as part of a broad reform package.

The Senate proposal was promoted by four Democrats and four Republicans – the famous 'Gang of Eight.' Graham was one of the group's members.

Now that friction over the Obama-era Deferred Action for Childhood Arrivals (DACA) program has made immigration the latest existential linchpin to hit Congress, old resentments are surfacing.

'His view of immigration has never been in the mainstream of the Senate,' Graham said of Miller as negotiations to end a government shutdown fell apart Sunday.

'And we're never going to get there as long as we embrace concepts that cannot possibly get 60 votes. So Mr. Miller has evolved on a pathway to citizenship, but for every green card you give a DACA recipient, he wants to take one out of the system.'

Miller, a loyal Trump adviser, used to staff then-Senator Jeff Sessions on immigration and was credited for helping to kill the moderate 'Gang of Eight' proposal in 2013

DACA is a guarantee against deportation for millions of illegal immigrants who were brought to the U.S. as children. It's set to explire in a matter of weeks and has become the GOP's biggest point of leverage as they try to win new funding for border security.

The White House said Sunday that it's Graham, not Miller, who is operating outside America's mainstream.

'As long as Sen. Graham chooses to support legislation that sides with people in this country illegally and unlawfully instead of our own American citizens, we are going nowhere. He's been an outlier for years,' said White House deputy press secretary Hogan Gidley.

Press secretary Sarah Sanders said Monday on Fox News that 'it's ridiculous when a United States senator is calling out an adviser to the president.'

'We’'re doing our best to carry out what the president has laid out and to implement and communicate his principles, and Stephen's no different on that front that any of the rest of us,' White House press secretary Sarah Sanders told reporters

Sanders said Monday on Fox News that 'it's ridiculous when a United States senator is calling out an adviser to the president'

'This is the president's agenda. Stephen Miller is certainly part of that conversation and part of this process, but he's advocating on behalf of the president.'

Sanders told reporters at the White House that blaming Miller is 'a sad and desperate attempt by a few people trying to tarnish a staffer.'

'Stephen’s not here to push his agenda,' she said. 'He's here to push the president's agenda, like everybody in this building.'

'We’'re doing our best to carry out what the president has laid out and to implement and communicate his principles, and Stephen's no different on that front that any of the rest of us.'

Asked Monday if Graham is assigning too much influence to Miller, White House budget director Mick Mulvaney said on Fox News that 'the president makes the decisions about immigration in the White House. Period, end of story.'

Lindsey Graham tweeted Sunday that Miller holds 'extreme and unrealistic views'

Miller sees his role as helping to steer Trump toward achieving what he laid out as his immigration policy goals during the presidential campaign.

A senior White House official told The Washington Post on Sunday that the brash young aide has told colleagues that his 'consuming focus is to make what I know the president wants in an immigration deal a legislative reality.'

But Graham suggested Trump would be better off negotiating an immigration deal without Miller looking over his shoulder.

'The White House staff, I think, is making it very difficult,' he told reporters at the Capitol.

Graham tweeted Sunday that some staff in the White House 'hold extreme and unrealistic views. They hold us back from getting a solution.'