Donald Trump has reportedly postponed a planned speech on immigration this week amid questions over whether he no longer stands by one of the core proposals of his candidacy.

The Republican nominee was due in Colorado to deliver a speech in Denver on Thursday as part of a weeklong focus on immigration as well as to attend a $25,000-per-couple fundraiser in Aspen the same day.

Lydia Blaha, a spokeswoman for the campaign in Colorado, confirmed Monday to The Denver Post that the event would not take place as scheduled, and the campaign emailed supporters explaining that "the speech he was planning to give is still being modified."

He also reportedly cancelled a rally scheduled for Friday in Las Vegas.

Confirmed: @alivitali reports that Trump's planned Denver immigration speech is now postponed. Will not be this week. No reason given. — Mark Murray (@mmurraypolitics) August 22, 2016

BREAKING: Friday's @realDonaldTrump rally in Las Vegas has been cancelled, per campaign staff. No reason specified. #8NN — Patrick Walker (@PatrickWalker) August 22, 2016

The cancellations come as the Trump campaign pushes back on reports he was "flip-flopping" on his plan to deport the more than 11 million immigrants in the U.S. illegally. Trump first announced his support of mass deportation last August, and along with his proposed wall along the U.S.-Mexico border it became the centerpiece of his campaign and a major source of his support.

At a meeting with Hispanic leaders over the weekend, Trump reportedly suggested his plan for a deportation force was potentially up for reconsideration, raising their hopes he planned to find a solution "that respects border security but deals with this in a humane and efficient manner," immigration lawyer Jacob Monty told Buzzfeed News after the Saturday meeting . And Univision reported the planned Thursday speech would introduce a new immigration proposal that would include a path to legalization for immigrants without proper documentation.

Newly installed campaign manager Kellyanne Conway on Sunday suggested some wiggle room in Trump's plan, saying it was "to be determined" if he would still support the creation of a "deportation force."

"What he supports is to make sure that we enforce the law, that we are respectful of those Americans who are looking for well-paying jobs, and that we are fair and humane for those who live among us in this country," Conway said.

Conway's comments set off a firestorm of speculation that Trump was shifting to a more general election-friendly message. But on Monday, Trump insisted he had no intention of changing his stance.

"I'm not flip-flopping," Trump told Fox News. "We want to come up with a really fair but firm answer."

But as the campaign confirmed the postponement of Thursday's event, other campaign representatives who attended Saturday's meeting were less clear.

Helen Aguirre Ferre, the Republican National Committee's director of Hispanic communications, on Monday afternoon declined to answer whether Trump was changing his tune.

"He never said the word 'deportation' and he never said the word 'legalization,'" Ferre told MSNBC on Monday. "He was there to listen and learn. He didn't give any indication one way or another as to what he would be doing."

"They're working on their policy at this point in time, it has to be very strong and very firm, and has to be fair or humane," she added.

And on Monday, Conway said the plan to deport 11 million people was never set in stone.

"Even Sen. Jeff Sessions [R-Ala.], who was one of the first to endorse Donald Trump and is known for the immigration issue, he doesn't deport 11 million people in his plan," Conway said on CNBC on Monday. "In other words, what Donald Trump says is we need a fair and effective way to deal with the 11 million here who are here who live among us, at the same time protecting American jobs and American workers and also securing our borders obviously. But what he's saying is immigration is a very complex issue with a very complex solution."