Republican presidential candidate Donald Trump has said over and over he would force undocumented immigrants to leave the country as president. Now a meeting with a Hispanic advisory panel and statements from his surrogates are calling into question whether that's still the plan. (Sarah Parnass/The Washington Post)

As Donald Trump continued to mull his stance on deporting millions of immigrants illegally living in the United States, his campaign Monday postponed an immigration policy speech that the Republican nominee had told supporters he planned to give later in the week.

Trump on Saturday told a newly formed panel of Hispanic advisers that he would give an immigration policy speech Thursday in Colorado, and he invited them to attend, according to several participants. But the Denver Post reported Monday that the campaign halted preparation for such an event and told supporters in an e-mail that the candidate’s speech “is still being modified.”

Trump’s campaign did not respond to questions about the delay. Trump is expected to discuss “illegal immigration and border security” at a town hall moderated by Fox News’s Sean Hannity on Tuesday in San Antonio; it will air Tuesday and Wednesday nights.

On Monday the campaign also canceled rallies scheduled for Las Vegas on Friday afternoon and Portland, Ore., next week.

Republican presidential nominee Donald Trump speaks about immigration and refugees in the USA during a campaign event at the BB&T Center in Sunrise, Florida, USA, 10 August 2016. (Cristobal Herrera/EPA)

For more than a year, Trump has said that the nation’s 11 million undocumented immigrants “have to go” and that he would create a “deportation force,” likening his plans to mass deportations carried out during the 1950s under President Dwight D. Eisenhower.

But Trump has seemed to slowly soften his tone on the issue, and top aides have hinted in recent days that he might change his position. Trump’s newly installed campaign manager, Kellyanne Conway, has previously advocated creating a pathway to citizenship for illegal immigrants.

“We’re dealing with people,” Trump said during an interview with Fox News on Monday morning. “We have to be very firm. We have to be very, very strong when people come in illegally. We have a lot of people that want to come in through the legal process, and it’s not fair for them. And we’re working with a lot of people in the Hispanic community to try and come up with an answer.”

Trump wouldn’t say what that answer is but said he had not changed his position.

“I’m not flip-flopping,” he said. “We want to come up with a really fair but firm answer. It has to be very firm. But we want something fair.”

Fierce opposition to illegal immigration has been at the heart of Trump’s candidacy and appeal, so any change to his position on mass deportations could anger conservative supporters who were key to his unlikely success in the primaries. But such a shift could win over moderates and independents, especially women, turned off by Trump’s harsh rhetoric.

Conway said on CNN on Sunday that Trump’s stance on mass deportations was “to be determined.” Sen. Jeff Sessions (R-Ala.), a close Trump adviser, said on CBS that the nominee is “wrestling” with the issue but has not changed his position yet.

Last week Trump seemed like a different candidate on the campaign trail as he read from teleprompters, started rallies on time and made appeals to African American voters. Those changes are largely attributed to new campaign leaders who took over Wednesday — Conway as campaign manager and Stephen Bannon, who previously led the conservative website Breitbart News, as chief executive.

Trump seemed to begin this week with less control as he lobbed angry tweets early Monday morning at the hosts of MSNBC’s “Morning Joe,” Mika Brzezinski and Joe Scarborough.

“Tried watching low-rated @Morning_Joe this morning, unwatchable! @morningmika is off the wall, a neurotic and not very bright mess!” Trump tweeted at 7:21 a.m.

A few minutes later, he followed up: “Some day, when things calm down, I’ll tell the real story of @JoeNBC and his very insecure long-time girlfriend, @morningmika. Two clowns!”

Later in the morning, Scarborough responded on Twitter without mentioning the ripped-from-the-tabloids rumor of a secret relationship: “Neurotic and not very bright? Look in the mirror.” He also tweeted: “Thanks for watching. Morning Joe is enjoying it’s best ratings ever thanks to obsessed fans like you. GLAD.”

Trump also unveiled a new attack on Hillary Clinton on Monday urging her to shut down the Clinton Foundation “immediately” and return money that was donated by countries “they shouldn’t be taking money from,” including those that discriminate against women and gays.

In addition, during a phone interview with Fox News, Trump revived his line of attack on Clinton’s longtime aide, Huma Abedin, whose husband, former New York congressman Anthony Weiner, resigned his seat in 2011 after a sexting scandal.

“But what about the fact that Huma Abedin, who knows every single thing about Hillary Clinton — she knows more about Hillary than Hillary knows — and she’s married to a pervert sleaze named Anthony Weiner who will send anything that he has out over Twitter or any other form of getting it out,” Trump said. “I mean, she’s married to Anthony Weiner. She knows everything that Hillary Clinton is doing and she’s married to a guy who has no control over himself.”

Ed O’Keefe contributed to this report.