President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE’s abrupt decision to impose sweeping tariffs on Mexico is exposing rifts within his administration on trade and immigration, two core issues he has repeatedly pledged to tackle but where he has struggled to gain ground.

The surprise Thursday night announcement marked a setback for U.S. Trade Representative (USTR) Robert Lighthizer Robert (Bob) Emmet LighthizerWhiskey, workers and friends caught in the trade dispute crossfire GOP senator warns quick vote on new NAFTA would be 'huge mistake' Pelosi casts doubt on USMCA deal in 2019 MORE, who argued the plan could threaten Trump’s North American trade agreement’s chances of congressional approval, according to three people familiar with the situation.

“Lighthizer tried to make his case once and failed,” said one industry source, who requested anonymity to describe discussions with the administration.

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A USTR spokesperson said in a statement that Lighthizer “supports the president and what the president is doing” but did not specifically mention the new tariffs on Mexico.

Trump’s move was also a loss for business-friendly figures in the administration, such as Treasury Secretary Steven Mnuchin Steven Terner MnuchinHillicon Valley: DOJ proposes tech liability shield reform to Congress | Treasury sanctions individuals, groups tied to Russian malign influence activities | House Republican introduces bill to set standards for self-driving cars Treasury: Trump's payroll tax deferral won't hurt Social Security Treasury sanctions individuals, groups tied to Russian malign influence activities MORE and National Economic Council Director Larry Kudlow Larry KudlowMORE. Another industry source said Mnuchin, like Lighthizer, opposed the plan. Kudlow is reportedly away recovering from hip surgery.

A Treasury Department spokesperson said Mnuchin “supports the president’s position.”

Trump decided to threaten Mexico with tariffs on all of its imports as he grew increasingly frustrated with the number of migrants crossing the U.S. southern border, many of whom are seeking asylum, according to two people familiar with the situation.

“This is something the president has been bringing up for months and was kept at bay,” said the first industry source.

What, exactly, the breaking point was for Trump remained a subject of speculation in Washington, with some officials pointing to conservative media reports focused on major apprehensions of migrants at the U.S.-Mexico border. Others noted he teased the move during a diatribe against special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE and viewed it as an effort to change the subject.

Apprehensions at the southern border have risen exponentially since the early months of Trump’s presidency.

In April 2017, Trump’s third full month in office, the number of apprehensions at the southern border fell to its low point of 15,798, according to data from U.S. Customs and Border Protection. The figure has spiraled to over 100,000 in both March and April of this year, the two most recent months for which data is available. The April total — 109,144 — was the highest of Trump’s presidency.

The president’s threat is seen as a boost for advisers such as Peter Navarro and Stephen Miller Stephen MillerSpecial counsel investigating DeVos for potential Hatch Act violation: report Trump confirms another White House staffer tested positive for COVID-19 Biden pick creates furor, underscoring bitterness over Obama immigration policy MORE, who have championed protectionist trade policies and a hard line on immigration, respectively.

Miller for months has urged the administration to adopt more aggressive measures to curb the number of migrants entering the U.S., in part by engineering a purge at the Department of Homeland Security, and he vocally pushed the Mexico tariffs, according to a person familiar with the situation.

The tariffs were discussed in a meeting on immigration this week at the White House that was attended by the president, Miller and White House counsel Pat Cipollone, among others, according to the person. Lighthizer was not present.

Navarro was one of a handful of White House officials who appeared Friday on cable television to defend the plan, saying it should have come as no surprise given Trump’s insistence that Mexico do more to stop illegal migration.

“If you look at it from an investor’s point of view and a corporate point of view, what we have in Mexico is the export, one of their high exports, of illegal aliens. And it’s a criminal enterprise,” the trade adviser said on CNBC.

Sources in Trump’s circle don’t dispute these divisions. But they also contend that the issue also has to be viewed through the lens of the 2020 election campaign, where a continued hard line on immigration will be a central part of the president’s appeal.

“This is definitely a victory for Navarro and Stephen Miller, but this is also a victory for the campaign team, which can use this as another base issue,” said one GOP strategist with ties to the White House who asked for anonymity to speak candidly.

It throws a wrench into the administration’s biggest legislative priority: passage of Trump’s revision of the North American Free Trade Agreement (NAFTA), which has been spearheaded by Lighthizer.

The top trade official had formed a solid working relationship with Speaker Nancy Pelosi Nancy PelosiHoyer: House should vote on COVID-19 aid — with or without a bipartisan deal Ruth Bader Ginsburg lies in repose at Supreme Court McCarthy threatens motion to oust Pelosi if she moves forward with impeachment MORE (D-Calif.) that many in the administration and on K Street believed was yielding progress toward pushing the agreement through Congress.

They now fear that Trump’s new tariffs, combined with the White House’s decision to formally start the clock on the legislative process over Pelosi’s objections, could stymie that progress, with one industry source calling the moves “a one-two gut punch.”

Lighthizer was reportedly unenthusiastic about the decision to pressure Democrats on NAFTA, a strategy that is said to be favored by Vice President Pence’s team, according to The Wall Street Journal.

The Republican National Committee, which is closely allied with the White House, and the House GOP Conference both blasted out press releases this week accusing Pelosi of dragging her feet on approving the agreement.

White House counselor Kellyanne Conway Kellyanne Elizabeth ConwaySpecial counsel investigating DeVos for potential Hatch Act violation: report George and Kellyanne Conway honor Ginsburg Trump carries on with rally, unaware of Ginsburg's death MORE downplayed those fears, telling reporters that “we are fully confident that [the trade deal] could pass the House.”

Although Trump has pushed for tariffs on Mexico for months, administration officials and industry groups described a slapdash rollout that some believe helped contribute to the widespread backlash against the plan.

The White House issued a presidential statement and held a conference call for reporters after Trump announced the tariffs by tweet. But behind the scenes, there was a scramble to pull together the plan. Some key lawmakers, including Senate Finance Committee Chairman Chuck Grassley Charles (Chuck) Ernest GrassleyThe Hill's 12:30 Report: Ginsburg lies in repose Top GOP senators say Hunter Biden's work 'cast a shadow' over Obama Ukraine policy Read: Senate GOP's controversial Biden report MORE (R-Iowa), were not briefed, and major business associations were either not given a heads-up or told about it at the last minute.

Grassley, whose office said it found out about the tariffs on Twitter, called them “a misuse of presidential tariff authority” that could derail Trump’s NAFTA rewrite. That sentiment was echoed by business groups, with the U.S. Chamber of Commerce saying it might even sue to stop the tariffs.

The administration has sought to assuage fears that the skirmish over tariffs could spiral out of control, especially if there is little Mexico can do in concrete terms to meet the Trump administration’s demands.

Acting Homeland Security Secretary Kevin McAleenan has outlined three areas where progress could be made: tightening border security between Mexico and Guatemala; the Mexican government holding U.S. asylum-seekers on the southern side of the border while their claims are adjudicated; and tougher action against human traffickers and criminal gangs.

“Mexico should engage with us, and we wouldn’t have to take any additional steps,” White House press secretary Sarah Huckabee Sarah Elizabeth SandersSarah Sanders on Trump's reported war dead criticism: 'Those comments didn't happen' Sarah Sanders memoir reportedly says Trump joked she should hook up with Kim Jong Un McEnany stamps her brand on White House press operation MORE Sanders told reporters on Friday.

A person familiar with the process told The Hill that the new tariff move was “a graduated approach with an immediate exit ramp if Mexico does the right thing.”

Trump has said that the tariffs would be introduced at a rate of 5 percent on June 10 and would then rise by 5 points at the beginning of each subsequent month to a ceiling of 25 percent. The U.S. imported $346.5 billion in goods from Mexico in 2018, according to the USTR, and the country recently became the U.S.’s largest trading partner.