Republican presidential candidate Donald Trump announced late Sunday he'll be making a speech on illegal immigration on Wednesday in Arizona, after a week of speculation that he might be softening his promise to deport 11 million people living in the United States illegally.

The announcement of the speech, posted in a Tweet, was initially set for last week in Phoenix, but was pushed back as Trump and his team wrestled over the details of what he would propose. There has been debate within his campaign about immigrants who haven't committed crimes beyond their immigration offenses.

The candidate's evolving stance hasn't made it easy for top supporters and advisers, from his running mate on down, to defend him or explain some campaign positions. 

On Sunday, Trump’s campaign and his supporters were challenged again to explain the candidate’s evolving policy but appeared to find solid ground in arguing it was the opposite of Hillary Clinton’s plan.

“There are very few issues where they're more different,” Trump campaign manager Kellyanne Conway told “Fox News Sunday.” “In fact, Hillary Clinton is to the left of Barack Obama on immigration.”

Trump won the GOP primary largely by appealing to the party’s conservative base with vows to deport all of the country’s estimated 11 million illegal immigrants and to build a wall along the entire southern-U.S. border and have Mexico pay for the construction.

However, Trump has in recent weeks appeared to search for a less austere approach, knowing that he’ll need some support from Hispanic and other minority voters to win the General Election race against Clinton, the Democratic presidential nominee.  

Conway said Trump indeed wants to find “the fair and humane way” to address the issue, which includes whether to separate families to enforce federal law.

But she made clear that Trump still intends to build the wall and that he supports neither amnesty nor legalization for people who entered the country illegally.  

“We all learned in kindergarten to stand in line, to wait our turn,” said Conway, who argued Trump has stopped talking about a deportation “force” to remove people.

“Give Donald Trump credit for at least trying to address a complex issue and not pretending like Hillary Clinton does, that we don't have these problems,” she said.

The Real Clear Politics average of recent polls shows Clinton leading Trump by 6 percentage points. Such polls also indicate Clinton is ahead in some of the most competitive and pivotal states, with 72 days remaining before Election Day. The nominees’ first presidential debate is set for Sept. 26.

“The real issue is look at the two plans,” Republican National Committee Chairman Reince Priebus told NBC’s “Meet the Press." “Look at where Hillary Clinton is. She wants to put Barack Obama's immigration plan on steroids. The issue is that this is an election of choices: One, allow everyone in through complete amnesty, or number two, a tough plan that's fair and humane.”

The Clinton campaign argues that Trump’s plan remains as “dangerous” as before, despite efforts to make it seem different.

“He may try to disguise his plans by throwing in words like ‘humane’ or ‘fair,' " said campaign spokeswoman Jennifer Palmieri. “But the reality remains that Trump’s agenda echoes the extreme right’s will -- one that is fueling a dangerous movement of hatred across the country.”

GOP vice-presidential nominee Mike Pence said Sunday the main tenets of Trump's immigration plan will include building the wall, no path to legalization or citizenship and stronger border enforcement.

The nominee and Indiana GOP governor also sought to distinguish Trump’s position from Clinton’s.

“It is going to be fair. It is going to be tough,” Pence told CNN’s “State of the Union.” “He has said that very consistently -- the contrast with Hillary Clinton, who supports amnesty, open borders, who wants to implement executive amnesty again on Day One, even though the Supreme Court of the United States rejected it.”

Pence did not answer questions on whether the campaign’s position, as Trump has said, is that children born to people who are in the U.S. illegally are not U.S. citizens.

Native-born children of immigrants, even those living illegally in the U.S., have been automatically considered American citizens since the adoption of the 14th Amendment in 1868.

Pence also could not definitively say whether Trump was sticking with his vow to remove those living in the U.S. illegally, with the help of a deportation force.

“What you heard him describe there, in his usual plainspoken, American way, was a mechanism, not a policy," the nominee said.

Trump has focused lately on deporting people who are in the U.S. illegally and who have committed crimes. But who Trump considers a criminal also remained unclear Sunday.

Pressed on the question, Priebus replied: "I just don't speak for Donald Trump."

FoxNews.com's Joseph Weber and The Associated Press contributed to this report.