Donald Trump, fresh off a hastily arranged visit to Mexico where he met with the country's president, doubled down Wednesday night on his vow to build a "great wall" along the southern border -- and make Mexico pay for it -- while outlining a more focused mission for the deportation force he's promised to create.

In a speech in Phoenix meant to clarify his immigration positions after appearing to soften his stance, the Republican presidential nominee outlined a hardline set of proposals for tackling illegal immigration. He did not, however, definitively call for removing all illegal immigrants in the country.

Rather, Trump vowed to focus first on deporting the estimated 2 million "criminal aliens" on day one, while also prioritizing certain groups like gang members and visa overstays for removal. He said, though, that any illegal immigrant could be subject to deportation under his administration.

"There will be no amnesty," he said, adding that no illegal immigrant would be legalized without first leaving and coming in through the front door.

"For those here illegally today, who are seeking legal status, they will have one route and one route only. To return home and apply for reentry like everybody else under the rules of the new legal immigration system I outlined above," he said.

Trump said that America’s current immigration system “serves the needs of wealthy donors, political activists and powerful politicians."

“Let me tell you who it does not serve, it does not serve you the American people. It doesn’t serve you,” he said.

In his speech, Trump also promised to end "catch and release," to increase the number of ICE and border patrol agents, block funding for sanctuary cities, and create a deportation task force that he said would be focused on deporting criminal aliens.

He also promised to cancel President Obama's "illegal" executive actions, and to enforce current immigration laws and accused Democratic rival Hillary Clinton of not having a plan on immigration, saying she would give "ObamaCare, Social Security and Medicare to illegal immigrants, breaking the federal budget."

When he talked about deporting criminal aliens who had "evaded justice," he also said Clinton had evaded justice.

"Maybe they'll be able to deport her too," he quipped.

He told the crowd that there are some immigrants who will be unable to assimilate into American society.

“It’s our right as a sovereign nation to choose immigrants we think are the likeliest to thrive and flourish and love us,” he said.

Amid rumors he was considering softening his trademark position on building a wall on the southern border, Trump made his position very clear.

"We will build a great wall along the southern border," he said to cries of "build the wall" from the boisterous crowd. "And Mexico will pay for the wall."

He later said the wall would be "impenetrable, physical, tall, powerful, beautiful."

Trump’s speech comes after he met with Mexican President Enrique Pena Nieto earlier in the day and asserted America’s “right” to build a border wall during a hastily arranged visit to Mexico City.

While both leaders adopted a measured and respectful tone, with Trump calling it a "substantive, direct and constructive exchange of ideas," there was disagreement on the question of the wall.

While Trump told reporters “we didn’t discuss payment of the wall,” Pena Nieto later contradicted Trump and said the subject was among those discussed. He also tweeted that he made it clear "that Mexico will not pay for the wall."

Trump has been accused of stoking tensions on the subject ever since he announced his campaign in June of last year in which he accused Mexico of not sending their best people across the border.

“When Mexico sends its people, they’re not sending their best. They’re not sending you. They’re not sending you. They’re sending people that have lots of problems, and they’re bringing those problems with us. They’re bringing drugs. They’re bringing crime. They’re rapists. And some, I assume, are good people,” he said.

In recent weeks, Trump has been accused of softening his tone on the subject, and had been forced to clarify whether he favored a path to citizenship for those here legally, and whether he still planned to build a wall.

The Associated Press contributed to this report.