Mexican President Andrés Manuel López Obrador dispatched his foreign relations secretary to Washington on Friday, as the country scrambles to negotiate a solution with the United States following President Trump’s surprise move this week to slap tariffs on Mexico in the hopes it would remedy the illegal immigration surge at the U.S.-Mexico border.

The president on Thursday announced the new tariffs, which are slated to go into effect on June 10. Trump said that a new five percent tariff would be placed on all Mexican imports to pressure the country to do more to help crack down on the surge of migrants trying to cross the U.S. Southern border. Trump warned, though, that the tariff percentage would gradually increase up to 25 percent “until the illegal immigration problem is remedied.”

"Mexico has taken advantage of the United States for decades. Because of the Dems, our Immigration Laws are BAD. Mexico makes a FORTUNE from the U.S., have for decades, they can easily fix this problem. Time for them to finally do what must be done!" Trump tweeted Friday morning.

TRUMP ANNOUNCES ESCALATING TARIFFS AGAINST MEXICO, STARTING AT 5 PERCENT UNTIL ILLEGAL IMMIGRANTS 'STOP'

Fox News learned that the tariffs, on all goods by land, sea, and air from Mexico will hike to 10 percent on July 1.

"If Mexico still has not taken action to dramatically reduce or eliminate the number of illegal aliens crossing its territory into the United States, Tariffs will be increased to 15 percent on August 1, 2019, to 20 percent on September 1, 2019, and to 25 percent on October 1, 2019," Trump said in a statement released later by the White House on Thursday. "Tariffs will permanently remain at the 25 percent level unless and until Mexico substantially stops the illegal inflow of aliens coming through its territory."

White House officials told Fox News that Mexico would need to step up security efforts on the border, target transcontinental smugglers, crack down on illicit bus lines and align with the U.S. on a workable asylum policy. Mexico could use certain so-called choke points on the Southern Border to curb illegal migration sharply, according to the sources.

But Obrador responded in a letter late Thursday, telling Trump that “social problems are not solved with duties or coercive measures,” and said that the United States has a history of being a nation of immigrants.

“The Statute of Liberty is not an empty symbol,” he wrote.

The situation could complicate the legislative passage of the United States-Mexico-Canada Agreement (USMCA), sent to Congress by the White House on Thursday, which has aimed broadly to limit tariffs among the three countries.

However, the White House told Fox News it saw the matters as entirely distinct and did not anticipate complications for the USMCA.

But the president was hit with pushback from several Republican senators Friday, criticizing the new tariffs.

“Trade policy and border security are separate issues. This is a misuse of presidential tariff authority and counter to congressional intent,” Sen. Chuck Grassley, R-Iowa, said in a statement Friday, warning that “following through on this threat would seriously jeopardize passage of USMCA, a central campaign pledge of President Trump’s and what could be a big victory for the country.”

Grassley urged the president to “consider alternatives,” such as “imposing a fee on the billions of dollars of remittances that annually leave the United States to Mexico”—something Grassley said “will only encourage illegal immigration.”

“I support nearly every one of President Trump’s immigration policies, but this is not one of them,” Grassley said.

OVER 1,000 ILLEGAL IMMIGRANTS APPREHENDED IN EL PASO SECTOR, LARGEST GROUP EVER AT A SINGLE TIME, SOURCES SAY

Sen. Joni Ernst, R-Iowa, also slammed the president’s decision, asking him to “reconsider.”

“If the president goes through with this, I’m afraid progress to get this trade agreement across the finish line will be stifled,” Ernst said in a statement. “While I support the need for comprehensive border security and a permanent fix to illegal immigration, this isn’t the right path forward.”

But Sen. Lindsey Graham, R-S.C., who has been a reliable ally for the president throughout his administration on a range of issues, supported the move.

“I support President Trump’s decision to impose tariffs on Mexico until they up their game to help us with our border disaster,” Graham tweeted. “The illegal flows from Central America must stop and Mexico needs to do more.”

Meanwhile, the president blasted Democrats for not being open to stricter policies at the border.

"Hard to believe that with the Crisis on the Border, the Dems won’t do the quick and easy fix. Would solve the problem but they want Open Borders, which equals crime!" Trump tweeted Friday.

Fox News’ Gregg Re, John Roberts, and The Associated Press contributed to this report.