WASHINGTON — For the first time since declaring his presidential run, Republican Donald Trump offered an extended apology to those who may have been hurt by his caustic comments, saying that he regrets some of what he's said “in the heat of debate.”

“Sometimes in the heat of debate and speaking on a multitude of issues, you don't choose the right words or you say the wrong thing. I have done that,” the GOP nominee reading from prepared text, said at a rally in Charlotte, N.C. “And believe it or not, I regret it, particularly where it may have caused personal pain.”

He added: “Too much is at stake for us to be consumed with these issues.” As the crowd cheered, Trump pledged to “always tell you the truth.”

The remarks came as Trump makes significant changes to a campaign that has struggled since the Democratic and Republican nominating conventions from self-created distractions.

Earlier Thursday, Trump moved to invest nearly $5 million in battleground state advertising to address daunting challenges in the states that will make or break his White House ambitions.

The New York businessman's campaign reserved television ad space over the coming 10 days in Florida, North Carolina, Ohio and Pennsylvania, according to Kantar Media's political ad tracker.

Democrat Hillary Clinton has spent more than $75 million on advertising in 10 states since locking up her party's nomination.

Trump trails Clinton in preference polls of most key battleground states. And his party leaders, even at the Republican National Committee, have conceded they may divert resources away from his campaign in favor of vulnerable Senate and House candidates if things don't improve.